The mortgage payment is $1,000 on each house, so you earn $500 per house or $2,000 monthly.

I also recommend to talk to the contractor in person because there's for us it's a gut feeling if we feel we can trust someGood luck.

I’m so glad I trusted my gut.Is this the norm for companies to charge for educational services to purchase tax liens.

Then, of course, visit real property/tax department for past due/current payment status of all taxes.

This might reduce your payment by half!  

Often answers are scripted and your job as an investor is to ask the right questions in the right way to answer for yourself whether you can trust what you are hearing.

If your contractor chose Bank of America for their business account then they should have asked about and discussed timing and fees for different deposit types before choosing, ask their clients to use Zelle, or have a separate payment service like one contractor I use has pocketsuite for estimate, payment and invoices.

Any suggestions how I can take a credit card payment from this individual?  

It takes time and you have to be good at building friendships and trust.

Your household names: Ernst and Young, Deloitte, KPMG, etc all offer audit services, as do your regionals like Grant Thornton.A full audit will typically consist of spot checking everything from invoices/receipts tying out to specific checks paid by accounts payable, and down to leases being input into the system, and tying rent payments to cleared checks.