A couple of extra points.
The original poster talked about having a pond dug out and installed. Guess what. The guys who do it, no matter how carefully they try, will only be able to "rough in" the ditches, berms and swells that you will need to keep water draining into the pond without having massive erosion. Since they use large equipment, they can only rough it in.
If you do not finish it up properly, then in just a matter of weeks, you will have deep erosion trenches in your land, plus overflows of the pond above the berm, etc. etc. It is impossible to fix this by hand with a pick and shovel. For this reason alone, you need a tractor with an adjustable scraper blade.
The other great thing about a 28 to 35 horsepower tractor, is that you can buy a four foot wide tiller to hook to the back of it, and it will easily till soil 4 inches deep in a four foot wide swath. Believe it or not, I use to plant two acres of grain every year, to let stand for the deer, and I used this tiller to till the entire 2 acres. It took me about 90 minutes per acre, for the first pass, and then about 30 minutes per acre to do a high speed second pass to break up the clods.
As noted before, you need to buy a second, small sit-upon mower, new or used, to actually "mow" grass around the house. It is quick and cheap. And, the main reason is that you do not want to have to spend 30 minutes in the scorching sun trying to hook and unhook a larger mower or bushhog to the back of your tractor every time you cut the grass.
Hope this helps.
Mannyrock