Craigslist.

I am always on craigslist free section looking for free stuff, plants too.

As far as the mulch, check with tree contractors. Some of them chip up branches, and have to pay to dump it. I'm sure you could talk them into delivering a load or two to your house if its free for them ;) But definitely mulch. I didn't believe the benefits of mulch until I mulched my back yard.

Make sure you amend the soil as needed. If the soil holds decent moisture, then that will help extend watering needs.

Weed free. Mulch helps keep weeds down, but some end up popping up anyways. Keep weeds out of the root zone. They compete for water with the plants you want to grow.

Drip irrigation. Water directly to the roots.

Research what plants are native. Natives naturally do better.

Are you going for edibles?

As far as the septic, there were giant yuccas planted over my leech field. I tore those out, and planted avocados a bit farther back. It's just mostly me here, so I'm not worried of the ick factor when it comes time to eat the avocados.

Can you reroute the washing machine drain to the yard? I did to 2 dwarf citrus (grapefruit and lemon). It's water that's already paid for, so why not? When the avocados get bigger, and their water needs increase, I'll extend the drain.

I'm not good with plant selection since I've been turning my yard into edibles. I do have roses, and they do take a significant amount of water.

Can you collect rainwater? I bought 2 330gal totes and hooked them up to my downspout. So far after 2 days of off and on rain I have about 400 gallons already. That should help between dry periods/summertime. Help get to the next rain period.

That's all I can think of for now. That's all I've done, and so far, having all my fruit trees and plants haven't cost me any extra water which costs money. But what I've learned is, it takes money to save money. I spent ~$800 on the water totes/ barrels/drip irrigation, but I don't have to rely on city water, and in the end my fruit is free.

Good luck and keep us updated :)

Many cities offer free mulch to residents;
here, we have to bring a driver's license or other photo ID & a water bill to prove that we live in the city, & show up at the designated place during the designated hours, & the backhoe guy will scoop up the mulch & dump it into our pick-up trucks or trailers.

This is a perfect time of year for starting new plants & gardens, as the plant swaps are gearing up.

Go to the Southern Gardening Forum, & click on "Exchanges" just above the messages, & look on the Exchanges page for swaps in your area.

Also, check your local gardening clubs, high schools, Master Gardeners, etc;
many of them have swaps, too.

Post a 'request' or 'want' on your local freecycle (I always try to post an 'offer' every time I ask for something, just good karma/balance/order in the universe kind of thing & it makes me de-clutter!).

Ask for surplus plants, especially of the 'cannot be killed' variety, & offer to dig or get one of your roommates to dig.

Many times irises, cannas, liriope, vinca, etc get crowded & older gardeners welcome someone to thin them out.

This discussion might have more ideas for you about mulch.

Trying to tackle this whole thing at once sounds overwhelming. For now, I would pick an area or two to rehab, and just keep the rest mowed down to a dull roar. Start smothering stuff you don't like - that can be smothered. Bamboo will need much more convincing than that to be killed, unless you have sheet metal to put over it with cinder blocks to hold it down. Some kinds of bamboo would not be stopped by that either.

IMO/E, It's much better to start with a clean slate than try to battle existing weeds while squeezing in plants you actually want.

To smother stuff that's not as strong and tenacious as bamboo, mow everything as short as possible, then cover with newspaper, at least 6 sheets thick, or cardboard, overlapping at the edges. Then cover with - whatever you have available - mulch, leaves, pine needles, kitchen scraps, coffee grounds, yard trimmings, at least thick enough to cover the paper completely, but preferably much thicker. And, I'd usually say, the contents of the mower bag. In your case though, doing that would probably add a lot of unnecessary weed seeds to beds. Once those have had a chance to sprout, and mowing is happening regularly, then it should be safe to add lawn clippings to beds. I might wait until early next summer to start doing that.

Whatever you have that will hold the paper down, and block the light from the weeds under, and then also decompose just like a store-bought shredded wood mulch would. I'll be doing a lot of this also, *again* after we move this month. It's best to wait a couple months to make sure the stuff under there is dead, before digging in to add 'good plants.' If you use a shovel to cut and edge to separate lawn area from bed area, the connections from the grass in the lawn to the grass under the smother will be cut. That's probably necessary if your grass is similar to mine. Then a border of some type, like landscape timbers or bricks, will help keep the grass from invading the bed, and give you something to weed-wack against, or you can make the effort to make the barrier slightly buried, so the mower tires can ride along it, eliminating the need to trim the edges. Patrol the borders when you mow/trim for anything going under the border, and pull while it's still easy to do. If a low spot is continually allowing grass under, I fix that.

This far south, you may find that many plants that say full sun can actually be overwhelmed if the sun really is shining on them all day. When starting from scratch, using mostly annuals the first year can be a good idea while you learn the patterns of light, observe windy spots, etc... The next thing to consider is the big stuff, the trees. Will you be adding or removing any? Then consider the shrubs. When you have that stuff in place, it should be obvious what little flowering plants should/could go where - and you should have rich, fertile spots to put...

With that many people in the house, you will have something in great supply --- compost green materials!

Start up a compost pile(s) to help your overall yard results over time.

As for actual weeding, if buying weed-killing products is not in your budget, then you can just get in there and dig dig dig. Pulling up some weeds by hand is a tedious but still helpful way of making a particular yard look better.

Craigslist free section will probably have some of the things you need, including extra mulch that someone doesn't need anymore after doing their yard.

Another idea...

How many rocks do you have laying around your yard? I was looking at your plan. If you have free rocks, I would work on the elongated area at the top of the image. You would need to add trees and shrubs first. Instead of mulching, I would put down layers of thick cardboard and then add layers of rock over that. I would artfully arrange some larger rocks in the setup. If you wanted more plants, I'd dig some topsoil out of other parts of the yard or use compost and put that in places over the rocks to build up beds and then plant there.

I don't live in your area so I don't know what grows well there. I frequent the clearance sections of the garden centers and nurseries in the area. If you don't need immediate results, you can find great deals on perennials that have bloomed once already and trees that will grow back the next year. For instance, last fall I found the crepe myrtles that will grow to 25' and dessert willows for $8 each. I also found dianthus, huge mums, and various other plants for 75% off. As mentioned above, many gardeners would be happy to have their plants thinned.

If you can get a good bed started, many of the annuals are really inexpensive to keep going. All you need are a few plants and just save the spent flower heads for reseeding. If the bed is ready, you just need to seed them directly into the bed.

OMG. There is so much going on in your household that this must be overwhelming. Like others, I would start to smother weeds and unwanted grassy areas by layering with black plastic (cheap garbage bags work well) and let nature do its thing. Then maybe pick one small area that you will work on this spring/summer. Maybe a few veggies or some easy flowers or a flowering shrub. While you're seeing progress in this area, you'll likely start to get a vision for the rest of the yard. My backyard is a really challenge. After the expense of reseeding and grading, it has gradually given itself over to more weeds than grass. So I keep it cut low and let nature rule. I've managed to put in some beautiful bloomers over the past couple of years. Its a process and a reality check. Take it slow, breathe deeply and good luck.

True, plastic should kill anything under there, including the microbes that decompose organic matter and make soil healthy. An odor can develop from anaerobic decomposition of large amounts of fresh green material. Plastic must be removed to garden an area smothered this way, and isn't visually appealing while waiting. Newspaper or cardboard are usually left in place because they decompose, so can be covered with mulch when laid, for an instant 'finished' look even though it's only the 1st step. Smothering with organic matter like this encourages/feeds the microbes, not kill them, and decomposes the weed matter aerobically, no concerns over foul odors or creating lifeless soil. To have a great garden, you need 'good dirt.'

Pulling little sprouts as soon as you see them is easy. Pulling a big patch of something that's grown tenacious roots is hard and takes exponentially more time. Patrol/pull often and it should only take a few minutes. Doing that feels like you're mostly looking at your 'good' plants, because you are, bending occasionally to pull any sprouts you see. I usually leave them laying right where they were, to wither in the sun within hours and return their nutrients to the soil.

Once you stop any weeds from dropping new seeds for a whole year in a yard, you'll be amazed at how many fewer weeds you'll see in successive years. Control is easy to maintain, so much easier than to gain initially, so don't be frustrated by all of the work the first year, or lie to yourself by doing things like just breaking the tops off of perennials but leaving the roots. (If you 'pulled' it once but it's still there, it wasn't killed or pulled, just pruned - and now you know the root must be killed/removed for certain death to result from your efforts.) Pour boiling water on that root, or get a shovel, dandelion fork, something that truly has a chance of killing that thing/getting completely rid of it. Continuing to do ineffective things is a waste of your time, and ends up using more of it in the long-term, so do it thoroughly the first time, a few more minutes, but is then the only time you deal with that thing.

Birds, other critters, and wind will always bring unwanted seeds, but patches of weeds come purely from neglecting to pull something before it's produced seeds in your yard, often a single plant that can be 10,000 plants the next year if left to leave its' seeds.

The other primary area of concern is those that creep in from adjacent property. Sometimes a hard barrier is needed, a row of bricks, landscape timbers, to extremes such as a trench filled with concrete. Make the effort/expense of hardscape if possible and necessary to thwart a yearly or constant border battle.

Go extreme, complete, total, one year, truly getting rid of anything perennial at the roots, and not allowing anything to drop seeds, install whatever barriers or measures are necessary to enforce your borders, and then maintaining...

Lawn can be one of the easiest things to have on your property. I live in a neighborhood of non gardeners. Many of them have lawn from one lot line to the other with a small planting of shrubs along the front of the foundation of the house, and that's it. They rarely spend time in their yard. Once a week or every two weeks they mow and that's all they do. Some of them don't even water in dry spells, they just let it brown out until the Fall. No mulching, no weeding. They use a string trimmer along the fence line and they're done.

If you will continue to have back problems, and you want the kids to move out, you will have to be realistic about how much you can take care of yourself.

My DH has a bad back and has been helped tremendously by Physical Therapy and can still do some yard work now without a problem. Our kids are living on their own but they will help out with projects in the yard and in the busy spring or fall season.

As a matter of fact, doing yard work could earn a living for your unemployed room mates, while they are looking for other work. People on Craig's list are always looking for people to help with yard work.