I would look into their contracts in details.

Problem is, 10% down doesn't pay off our home equity loan.I tracked the buyer down and called him, and we sort of agree in principle on a deal, but the details are still fuzzy.

Buy something.There's 1000+ details omitted there for brevity, but to your question about "legal steps in terms of financing" that's the general answer. 

Your contractor and home inspector should give you the details on how to proceed. 

It's simple: He complies with the payment dates and method detailed in the lease or you move to evict him.

That being said, you can overcome some of the challenges of distance with technology, such as if you receive video (or photos) along with maintenance requests from your out-of-state tenants, allowing you to keep some visual on your property from a distance.If you are comfortable with distance, there is a price-to-rent ratio that may come in handy for you and end some of the analysis paralysis.

Details:1.

@Ivan Barratt - you are to blame for my descent into the K-1 details as you showed me just how little I knew about the topic but how critically important such knowledge is! 

Thank you for clarifying the details on a multi-family property.  

Unless you have a video of them smoking, you don't have much of a leg to stand on when you have to explain yourself.