A specialized commercial broker in a specific niche or any commercial broker?

Unless a property has a non-conforming use permit (NUC), there are only 4 areas on O'ahu that you can legally do STRS.  

If you are looking for Detroit-specific help, @Drew Sygit would be a good resource.

Time is money and I prefer spending my time with my fam and friends instead of problem tenants and legal cases. 

Specifically from the Caged AC Unit into the attic (concrete slab so no crawl space).I was thinking of just building a tall vertical box to place this into.  

it may be jurisdictional specific, but it would certainly limit the sources for providing credit reports.  

You are perfectly legal and right to do so.

Check Furnished Finder, Zillow, as well as AirBnb and VRBO (30+ day stays) to see what sort of competition is in that specific market.

I don't necessarily need the standard features of pm software, such as rent collection, bookkeeping and maintenance requests, though that could help; but do need a clearinghouse of important information, such as leases, legal docs and other information; maintenance vendors I use; maintenance history; and some kind of tracking system, where I can record the various current projects I'm working on within the business.

If you need financial help, ask under the "Finance, Tax, and Legal" forum.