Moving fish in the winter can be really dangerous. Their immune systems are 90% shut down when the water is at 50ð and the added stress of moving one will lower it even further. He could be attacked easily by parasites and/or bacterial infections. Plus if he is indoors now and you ware wanting to put him into cold water, the stress of that drastic temperature change could kill him. Large koi can handle that kind of stress much easier than a tiny little baby koi. Personally, I'd pass on this fish and wait until spring.

Thanks ccombs for the info.
I thought about it also nice koi but i will pass
thanks again.