You might also talk to a certified arborist in your area (not just a "tree-cutting guy"), as he/she would know how the city or county handles this type of issue on a routine basis.Here (very common), if it's over the property line on your side, you can chop it.I'd make a documented effort to contact the owner regarding your concerns; sounds like they don't care & won't respond, anyway.

Eventually it just kind of becomes a routine task when screening roommates.

Wow that must be a very uncomfortable position @Paul StoutAside from RE what are your instincts telling you?  

Yes I'm fishing for the broad scope so I can mix it all up and revise my own routine.

(outside of the people you already know routine)2)And what is the best way to find retail tenants for a small strip shopping center?

Issues such as water drainage around the foundation, repaving the parking lot, and routine interior rehab are on the list.I already got quotes from contractors for several big repair jobs.

That's routine day to day stuff.Nonroutine things include dealing with a deceased person and their belongings. 

Since then, I've been able to re-use my knowledge from that renovation to buy the right materials for my other four multi-units, communicate with and manage contractors confidently, and take care of routine maintenance issues when they arise. 

Things to consider and look out for; Houses in that area can still be on wells, Radon is something to test for, Sewer scoping is a good idea, other than that, pretty routine.  

@John T kemper local chamber of commerce will routinely have this type of info.