To do this legally, I know plans need to be drawn and submitted to the Planning Board.

I hired a surveyor,  engineer and ran through the process with the city myself. 

Would you rather set it and forget it and not need to refi again or rather take advantage of low/no closing costs on this loan and plan to be more aggressive on your rate at the time of your refi?

I spent my first 6 years in the financial planning industry working for a firm that had previously sold a lot of privately held REITS that went south.

I currently work with a handful of investors and love the process A-Z.

A common pitfall is treating each deal as a standalone transaction instead of connecting acquisitions, financing, and project management as part of one cohesive process.

If you are comfortable with the rezone process I would look at this, and perhaps you can still ADU in future after the rezone.

I'm in the process of vetting some seller financed deals for my solo401k portfolio.

Well I may not be the most seasoned in the world but my wife and I have established processes that work for us. 

Ensure you collect a proper security deposit (typically one month's rent in Florida) to cover potential damages.Your plan to increase rent next year makes sense given rising costs (taxes, insurance, and maintenance).