When that tree was very young, it had a bamboo stake tied tightly to the trunk to force it to grow straight. The stake was left on too long and rubbed the trunk raw.

The trunk has healed nicely, and should be fine. I would be more worried about the condition of the roots inside that pot... are they wrapped around and girdling? Also the tree is planted too deeply in the pot. You will need to correct the depth when you put it in the ground.

With all that going on, I would pass and continue looking for a good specimen. Even if it means waiting another year when fresh stock will be available.