I'd suggest a long conversation with someone actually doing these types of investing, (there are actually variations), in which a forum conversation leaves out, a lot you need to know. 

I'm doing a simple 20X20 ADU garage conversion (400 sq. ft).

I've read through the General Plan and there is nothing else that broadens or limits this description that I can find.Generally speaking, does this mean that I should have ministerial approval to perform a condo conversion of these already-built-out units in the same sense that I would have ministerial approval to submit plans for a new construction condos if the land were still vacant?  

@Raekwon Yates following this conversation, I have a wholesale company based out of DC and am looking to relocate to PR

So he claims the only way to meet the equitable interest/equitable title/equitable conversion element under the new SC law is through an installment sale. 

Every strategy you described, gets you less than a 0.1% conversion rate.

As for the rental, generally, we'll need to register with the city and they might come with inspection (happened twice to us) so make sure that the conversion is up to code and the list of the requirements are met. 

My suggestion is you can do a lot of networking + conversation's virtually.

I am thinking anything from simple level camping pads for tent, van conversion, or RV use.

I appreciate the encouragement to bring a historical perspective to the conversation.