A lot of folks on this site are wicked smart and do well with complicated formulas.My first "go to" formula is:  offer price <= (potential rent) x (50) - (rehab cost)For example:  offer price <= $2100x50 - $5000 or $100,000You can move your "50" number up a bit if you want. 

The tax status should not be affected unless you convert from a tax deferred to a tax free for example.

For example, the loan could have no payments due in the first 12 months.

And your seller would be able to go into their next deal with an all new basis and fresh depreciation.

For example.

Tax on the income is either deferred (Traditional IRA) or eliminated (Roth IRA).Rental real estate is an example of a type of real estate investment that can be a tax shelter on its own.

When we identify a problem (for example: a fire hazard in the electrical panel) we'll recommend a specialist (an electrician) to fully evaluate the problem and prescribe the most appropriate fix.Back to your specific question:  if the basement walls and ceilings are covered it will be difficult for anyone (including a structural engineer) to evaluate for structural issues. 

Ie $9,000 in your example if I paid 90% UPB.  

I'd view the latter as having more tenant turnover for example but the former is much more costly to buy into.

For example, would you pay $100 for a half consumed bottle of water?