Foundation settled but not cracked. Should I fix?

[Aroldo Villarreal]

I am working on a single family home in which the foundation repair is going to be $5,300. The seller agreed to reduce the price by $6k since he didn't know there were foundation problems. Every window and door opens and closes easily. There are no wall cracks and the floor feels level. I spoke to another investor and he said that it is difficult to find a level home in San Antonio because of the soil. He says he doesn't fix foundations in his rentals if the doors and windows work perfectly and there are no visible problems. He said there's a difference between the whole foundation settling and the foundation cracking, which I think makes sense, but don't have experience. What would you do?