I don't know about Florida's zoning laws, but here in Oklahoma, if the zoning allows horses at all inside the city limits, you have to have a minimum of 2-1/2 acres. Guess it has something to do with the manure. My aunt in Tulsa had a neighbor with two horses on 2-1/2 acres, and they had to feed hay all year round - there was some grazing, but not much. Then again, they didn't take very good care of the place, either.
We live in a very rural area with no zoning laws. We have 15 acres and five horses. It's not nearly enough, in my opinion, since a lot of the pasture is still covered in trees. What pasture we do have rehabbed - about 4 - 5 acres - still won't feed the horses full time - they can graze it down quick! It went from knee high to about 2 inches tall in less than a month, and that was with seed and fertilizer.
In you situation, the more land you can get, the better off you will be. If you only are able to have an acre or so in pasture, be prepared to do the mainanance required - you'll need to clean up the manure daily (trust me, if you don't, it will get ahead of you very quickly - that's the voice of experience!). You will need to keep it mowed to keep the weeds down, and then there will be seed and fertilizer - a constant expense - and you will need to be able to keep the horse off of it to let it get established and/or regrow. If you have two acres, that would be better, or at least be able to cross fence it so your horse can graze one side while the other is recovering.
My daugher is 30 years old, and frequently whines about how much work is involved in keeping the horses. She didn't realize just how much work was involved...if she had known in advance, she might have decided not to buy any!
Plain Old Dee, horses Dancer and Rain I believe in dragons, unicorns, good men and other mythical creatures!