I heard that short term loophole is a one time benefit that you get the year you start service.

You can build you life in tax avoidance, debt refi....  

All my houses currently have good tenants that pay on time.

You may also have the owners stay on {part-time} for a season or two to help train the new management (you).Acquire the hard assets:  In this scenario you would only purchase the real property and those hard assets (docks, boats, etc.) that you deem would be beneficial.  

David,Reach out to @Lucia Rushton I have worked with Lucia several times and as a seasoned agent she has an a solid track record of finding good cash flowing STR's. 

This strategy often will cover most, if not all of the actual mortgage, while you fix up the other half or life there (in your case school). 

Is FHA a complete waste of time in this area vs. conventional financing?

Cost segregation is a popular tax deferral strategy and there is often confusion as to the difference between bonus depreciation and reclassification.Bonus DepreciationBonus depreciation is a tax incentive that allows a business to immediately deduct a large percentage of the purchase price of eligible assets, such as washers and dryers, rather than write them off over the "useful life" of that asset.

You can't say "the home is listed at $500k for easy math and homes newly renovated are worth $800k." and expect that to be real life.

The county you live in may require code inspections if utilities have been off for an extended period of time.