Research what other properties they own, always check if property taxes were paid timely on their properties (on the assessor's site), look for signs of financial distress or life circumstances driving the need for a quick sale (divorce, probate, etc.).I bought several properties from a bankruptcy situation.

This may get a little complicated so bare with me, the seller filed for bankruptcy last year.

I assume you don't have a foreclsoure, or bankruptcy in your past what about collections and judgments.

Does a personal bankruptcy affect investors with S corp or C Corp?

Owner filed bankruptcy a year ago but they are still showing.

However, this introduces new issues like bankruptcy risk, calls from lenders when property is taken subject-to, etc.

What happens if they declare bankruptcy?

You could really get in a wringer if you charged the card on the 15th and they filed for bankruptcy on the 14th without your knowledge.

Is there any way that said lender could protect their position so that they aren't wiped out in a bankruptcy?

You could put together a 5-year business plan - which ends in bankruptcy.