We had to treat professionally twice, scrub everything down, take off all the electric covers and vaccuum out the wall receptacles, throw out the fridge, Kilz and repaint, rip out all the carpet and patch & refinish the hardwood floors underneath.

I would encourage you to treat it like a business. 

It sounds like I need to treat this tree the way you did my artistic hopes and dreams :)

Personal use also includes time spent at your place by another party under a reciprocal sharing arrangement (“I use your place in exchange for you using my place”) whether the other party pays market rent or not.Days devoted principally to repairs and maintenance are considered days of vacancy and are disregarded, even if family members are present while you work away.The tax drillVacation homes in this category are treated as personal residences for federal income tax purposes.

If they falter you need to evict them.You should never let someone get this far behind on money they owe you.My lease says any money owed is treated as past due rent and any payments received is applied to oldest amount owed.

If you buy and he renovates, I would just treat him like a contractor and pay him for his services.

I notice a lot of new landlords think "I'm just going to treat the tenants the way that I would want to be treated", and as many of us know, that is a recipe for disaster both in terms of management headaches and running afoul of landlord-tenant laws. 

Then start treating it as your own property. 

If they sue you in small claims, you can show that you were making a good-faith effort to replace them and they were treating them in accordance with the lease and the law.

Tenant was stung by a bee or wasp in the yard and is requesting owner to treat the yard.