I think you ought to incorporate before your first deal so you can protect yourself and your personal assets.  

Is there anything I can do to protect myself other than bringing it up to my lawyer and asking him to do a thorough review?

PM if you wish and I can send over some general guidelines to help protect his investment and perhaps get you closer to a reasonable deal.

My true passion is trains and I have made something out of myself in the hobby with custom painting, weathering etc.

I've also got 3 customer homes closing in the next couple weeks, I need to design and plan the renovation for my student rental that we closed on last week, I just wrote an offer for another property to flip and hopefully I can help @Kerry Baird to buy the house that's coming up for sale 2 doors down from mine!

At the end of the day, they are your customers.

Make sure that you have an attorney involved to draw up the loan docs to ensure that everyone is protected.  

Not that it is always pleasant, but I'm the buyer, the customer--not the employee--just own it.

Remember that long leases protect the tenant, not much the landlord.

I am looking for a legal way to protect myself against the owner changing his mind and living in a newly remodeled home financed by my money.