I have 6+ acres in Florida with horses on the property. Also starting a small tree nursery, 30Gallon size or less. I want to buy a small tractor I can handle myself to do the "big" jobs.
Mowing pastures (must mow at 6" minimum)
Moving dirt/manure/hay
Grading
Possible auger for post installation (fencing)
main concerns: fair price, dependability, service availability, operator comfort
Wow! Isn't Clermont, Fl one of those places you have to be careful not to dig a posthole too deep or it turns into a well?
When you say "must mow at 6" minimum," does that mean that you will not want to mow anything below 6", or is that the average height of the grass in your pasture? This sounds like a rough cut rotary mower would be ideal. If you aren't looking for a golf course quality lawn, the finish mower just doesn't make sense to me. Finish mowers, and especially belly mowers, are very expensive. I tend to agree with jimmyj, who suggested you spend that extra money on a stand-alone rider for those truly finish mower chores. You can get a nice 54" wide deck on a ZTR for the price of a belly mower. That mower will do your lawn and your pasture touchup where needed. Of course, only you know for sure what you want/need, so this is just me making a suggestion.
What about the form of your hay? It is very important to know whether you are talking about square or round bales when you are looking for a tractor to move them. Round bales take a whole larger class of tractor to handle than do square bales. Since you will have horses, I'm guessing squares are the type of hay you will feed. In that case, almost any tractor will haul a few bales.
Light dirt work is also easy to do with small tractors. moving loose dirt/gravel/manure and grading can easily be done by sub-compacts, but don't expect to change the landscape with them unless you have nothing else to do for years on end. The real key to what you need for your trees is how much the trees will weigh and how wide the rows will be so you can drive your tractor into your tree farm. Everything takes planning, planning, planning. It'll make you pull your hair out.
Find out all the specs of any tractor you will buy. What is the maximum lift of the 3PH and FEL? How high can you raise the FEL bucket and is the 3PH big enough to handle full-sized implements. Take the lift specs of the tractor and divide them by two to find the "working" values. If 80% of your work will be in this 1/2 maximum range, you will be much happier with your tractor's performance. Also, you will NOT be happy with a small 2wd tractor with an FEL. If you get a tractor with an FEL, stick with 4wd. You'll never be sorry.
You really want to stay away from the small cat-0 implements in my opinion. You will find many more used or even new implements available for cat-1 than cat-0. That means you probably should not look for a sub-compact. I would suggest something in the 25 hp to 35 hp range. If you can't afford new, then just keep looking for used. I also believe you will be more productive a lot quicker with a hydrostatic transmission, but don't overlook the gear models since you are on a very limited budget.
It's a lot easier to find info on new tractors than used ones, but if you find something that interests you, just ask here and somebody will be able to give you the info or tell you where you can find it. It's exciting and scary to be tractor shopping, perhaps also intimidating for you. Trying to decide whether to buy from a dealer or and individual can be a huge dilemma. I would say that whatever brand you buy, be sure you can get local support. Stay with brands you see at major dealers and you will be safer. You don't have to buy from the dealer, but I'd sure feel a lot better buying a known tractor model from an individual that buying an unknown brand from a strip shopping center dealer who just opened in the last month.
Welcome to TBN. Good luck, and keep us posted.