Condition and equipment are relatively minor factors.

Doing this will prolong the life of the hvac equipment.

Per this link: http://codes.ohio.gov/orc/5321.04"Supply running water, reasonable amounts of hot water, and reasonable heat at all times, except where the building that includes the dwelling unit is not required by law to be equipped for that purpose, or the dwelling unit is so constructed that heat or hot water is generated by an installation within the exclusive control of the tenant and supplied by a direct public utility connection".You're still supplying it, they just don't have access to change it.

Tell them that the police are best equipped to handle this type of situation and that once appropriate steps have taken place, you will then be able to discuss this matter directly with the upstairs tenant.  

Anything shorter than that will reduce the useful life of your equipment.  

This is to say that there is no appreciable market demand for PV equipped rental property for the purpose of being "green".

We also pay extra for sanding, but many won't take on the liability for sanding and the equipment is expensive so it's harder to find people to do it. 

It's fall all the tree guys are still out and some work in the winter. better time to fall some trees because won't damage the ground if its frozen for removal as much, if heavy equipment is needed.Get a couple of bids go on craigslist just make sure they have insurance.Let the neighbor know about the work, if it's close to their roof line and over property line. and ask if they have a tree guy.I'd do the work less trouble in the future and make sure that they give that tree a good trim, 

A possible deal breaker / ball buster: Cash buyer ready to go to contract and offer pending acceptance included my home based ornamental plant nursery biz (Ebay 'PowerSeller' online store, website, the works) plus attached greenhouse, attached nursery stock inventory, attached equipment, etc.

If you go to a 90% or more you would have to change flue piping and that would cost more in labor and for the equipment.