Rebuilding SFH to MFH Affordable Housing on Small Lots?

[David Hume]

I currently own 3 properties free and clear in Miami-Dade county. They're not in a great part of town and I rent them to section 8 tenants. However, they are all zoned RU3, even though they are currently just housing a single property. They are 2 50x140s and one 50 x 120. 

These structures were all built in the 1950s and they, quite flatly, suck. 

I wanted to know if anyone has had experience converting small properties like these to MFH's and if they have any affordable housing programs they recommend or if they know builders. 

I want to hold these long term, but I think I can get much more rental income from putting more tenants on them.