Now I feel I need to get someone else involved who knows the market well, but I don't want to pay a full commission for a negotiation that seems relatively simple - and I'm not eager to introduce another party into this situation.Many people have purchased these types of investment properties.

If that works for both parties, do it.

The landlord signed on the spot and both parties were happy.

That said, for some work in some municipalities, a licensed party must be used to pull certain permits with building and safety.

Payment may not be made by third party checks.

What if any of these negative scenarios are simply perceived by the other party?

You can do whatever you want as long as all parties agree.

If it goes sideways you want to have a solid commercial lease that spells out everything very clearly and has all of the tenant parties responsible for the lease.  

Perhaps a nice 1950's built bungalow.Always hire a 3rd party property inspector to give you an unbiased feel for the home.

Also, your corp is going to buy it from you with 20% down and a loan from a third party lender, correct?