How did you verify the rent being paid?

No legit buyers want their time wasted, so, in the words of Ronald Regan......trust, yet verify.  

When I verified her employment, she works at a grocery store that I think her husband or family owns.My spidey senses are telling me she is renting my condo for her daughter....I'm really on the fence about renting to the applicant...what would you do?

At the end of the day, you have to verify everything the seller is telling you especially if you have never transacted with them.  

I have checked the tax records and verified he is the current owner and taxes are up to date.

I also don't know how I could verify numbers (a.g. the amount paid to the wholesaler), since there is no HUD involved as it is a cash sale.

I'd never trust the numbers of a homeowner, unless they were a licensed contractor themselves, and even then, I'd double-check and verify everything myself.Since you don't know any contractors, I'd reach out to your network (friends, family, coworkers) and ask for references.

Make sure you triple check and verify your numbers though because you’ve thrown out 3 completely different values all in one discussion.

One thing I am trying to figure out though is how to properly verify all the tenants are actually...1.

Are you just trying to verify the potential rental value of the property for when you're no longer living in the property?