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?

An LLC is a good device to hide your identity behind. 

After sending the wire instructions to the title company to verify they were correct, they told me to call my bank ASAP and report it because it wasn’t their wiring info.

They'll also verify all current year income and ask for a YTD profit and loss statement from a CPA.

I would encourage you to verify that any first time home buyer program you use will be available for an investment property and not just for owner occupied loans.