Concentrate on knowing local market dynamics, financial planning, legal and tax implications, and long-term objectives.

This is not legal advice.

There are sections of Dunedin and northern Clearwater that are Unincorporated (and therefore legal) that will be quite close to Tarpon and be a much better investment.

Or legal advice - get with an attorney. 

Also pretty certain you have to have the proper licensing in most area to do this kind of lease structure legally...

Is it legal to do so?

I know a developer that has successfully gone full cycle using the San Diego ADU law that allows max AduS to legal existing space likely over 10 times.  

I don't like the terms and would try to avoid.We could still do a conventional loan and if I'm not mistaken it'd be this whole "gift money" thing so the shared ownership wouldn't be recognized legally.

nbi-sems.com (its for lawyers) but has great classes on the legal stuff behind title work.Also Attorneys guaranty title has a good class as well.

You and your wife would be getting a guaranteed income stream for the rest of your lives, which is not only putting money in your pocket, It’s also giving you a substantial amount of peace of mind in that you’re gonna get that money regardless, you have nothing left to manage and you have ZERO legal liability to worry about, freeing up a lot of mental space to just focus on fishing, relaxing, and doing just whatever you and your wife wanna do.