Newbie seeking guidance!

[Cameron Moore]

Hey everyone, I might have a way to get into investing and help out a friend of a friend. Quick backdrop, found a tax deed sale, taxes owed are 12k, and property is valued at 90k total (40k for land and 50k for the house). I have a chance to get a quit deed claim and pay off the taxes before auction. The original owner will continue to live there and pay rent. Can be plain renting or rent to own. Some concerns are if the original owner tries to make me pay for repairs that are pre existing like roof, foundation, etc and of course if they never pay rent. I know an FED can be filed but at what point? Also what is a fair rent price if I only have 12k invested? Any questions, comments, or concerns please let me know!