The lot is 17,502 square feet, and according to this zoning guide, if the lot is over 15,000 square feet, it appears that I can build more, as long as I adhere to the setbacks (page 15) http://www.orangecountyfl.net/Portals/0/resource%2..The back of the quadplex is 66 feet from the back of the lot, and the setback requirements are 30 feet for the zoning.

Or you can look at price per square foot and add or subtract based on the differences, keep in mind that typically the smaller the house the more per sq. ft. you'll pay.  

Sounds like you're ready to jump in and get your feet wet.

Where building setbacks exceed 100 feet (30 m) from the street or road, additional non-illuminated 4 inch (102 mm) numbers shall be displayed at the property entrance. 

James Bowie“The key to Evernote is to commit to it and jump in with both feet.

Then I think you should go on your merry way becoming a short-term lease mogul - but earn yourself a good name, and do things by the book.The Bigger Pockets community is a staunch advocate of playing by the rules fair and square, and your landlord may very well be one of our BP brethren who works hard to follow the rules to give you a fair and square lease.

If I'm using latex, which I almost always am, I move the feed hose over to straight water when I still have a few square feet left.

Are there any general contractors or others that have recently built that could ballpark the cost to build per square foot for me??

James Bowie“The key to Evernote is to commit to it and jump in with both feet.

When you are back on your feet house hacking would be a good first step to get into investing.