Hillsborough county opportunity zones, here is a helpful article. https://eig.org/news/what-to-know-u-s-treasury-announces-proposed-guidance-on-opportunity-zones

ADUs are allowed on lots zoned for single-family or multi-family residential use which contain or are proposed to be developed with a single-family dwelling.

Hit them up with your proposal.

So what I propose may or may not work in your situation and is based only on the information you shared in your post.You and tenant agreed to a move-out date of January 1, 2019 with an appointment for 4pm for the final walk-through and handing over of the keys.  

Call him back, tell him you are ready to talk and say you would like 5-10 minutes to go over your proposal and how about Tuesday.

I am a beginning real estate investor in NY and was recently contacted by an NYC wholesaler proposing to work on a joint venture "wholetail" deal in Bushwick, Brooklyn.

The purpose of my discussion is to propose my helping hands and additional energy to assist anyone within the state and city/cities with their properties or even company.

@Caleb Heimsoth Not sure if I know the mechanics of what you propose. 

Questions: Seller proposes to value the house at $85,000 and charge 5% interest for the first year, and incrementally increase the rate to incentivize the refinancing. 1) Is it likely that the buyer would be able to refinance within a three year period given his credit situation?

Putting together a proposal for seller financing could work out well to get you into those properties.