Appreciation is likely to be lower than on developed land, as population/housing is what drives demand in RE.Appreciation itself is speculation, NOT investment. 

In R-1AA, R-1A, R-1, R-1N and R-2A zoning districts an Accessory Apartment, Accessory Cottage, or Garage Apartment may beallowed as a second dwelling unit on a single-family building site under the following conditions:i) Accessory Apartment.(1) Inside the Traditional City, one Accessory Apartment shall be allowed as a Permitted Use when the building site is at least 1.5 times theminimum lot size for the applicable zoning district.(2) Outside the Traditional City, one Accessory Apartment may be allowed as a Conditional Use in accordance with the regulations andprocedures provided in Chapter 65, Part 2D, when the building site is at last 1.5 times the minimum lot size for the applicable zoningdistrict.ii) Accessory Cottage.(1) Inside the Traditional City, one Accessory Cottage shall be allowed as a Permitted Use when the building site is at least 2.0 times theminimum lot size for the applicable zoning district.(2) Outside the Traditional City in the R-1AA, R-1A, R-1 and R-1N Districts, one Accessory Cottage may be allowed as a Conditional Use inaccordance with the regulations and procedures provided in Chapter 65, Part 2D provided that the building site is at least 2.0 times theminimum lot size for the applicable zoning district.(3) In the R-2A district inside and outside of the Traditional City, Accessory Cottages shall be a permitted use provided that the minimumbuilding site area for an Accessory Cottage shall be the same as that required for a duplex development.

Until you know exactly where the flags or boundaries are you are way ahead of your self.A land not able to develop worth =0

As you get more experience, you can start to develop a general sense of what you need to budget. 

We are in the planning phase for a development project for a Quadplex in an Oceanfront lot.  

I'd see if you could partner with a realtor to sell to an end buyer as a turnkey custom home you'd develop for them if you can't wholesale it.

This area is in central Florida and the development over the past 5 years has been tremendous, both with home and job growth.

It would be a short term loan, maybe a year term, with 20% down making interest only payments with a balloon payment at the end when he gets a commercial loan to continue with his land development plans.

Develop some kind of outsized persona.Sophisticated family offices, institutions, and high net worth investors do not invest with sponsors based on their being boisterous, braggadocios, and having out-sized personas. 

This can be developed with intentional focus and consistent application.