I worked with someone whose two units shared a backyard and he did the kindergarten solution: drew a line down the middle and each unit had half!

You can take half of that and pay off the interest on the loan.  

FHA really is the easiest barrier of entry to overcome but as you've noted, it comes with its own obstacles. 

I am trying to find STR insurance coverage for 2 garage apartment units that I would like to use as STRs full-time and my house that I would like to use as a STR when out of town for work (maybe half the year).

I think granting them an easement would be quickest and easiest; quit-claiming the strip of land would be more expensive and complex. 

I am trying to find STR insurance coverage for 2 garage apartment units that I would like to use as STRs full-time and my house that I would like to use as a STR when out of town for work (maybe half the year).

One is a 3,800 square foot pole building, half of which is completely new due to a fire in the last few years, as well as a 2,000 square foot 2 story shop with it's own electricity, furnace, and ventilated painting spray booth.

One is a 3,800 square foot pole building, half of which is completely new due to a fire in the last few years, as well as a 2,000 square foot 2 story shop with it's own electricity, furnace, and ventilated painting spray booth.

I think house hacking is a great way to get your feet wet in rental investing, especially if you can find a duplex or so and live in one half and rent out the other half.

Being creative is half of the battle in real estate investing.