Hi All,
Been lurking awhile, and have really enjoyed the information, stories, and jokes presented here. I'm posting now because I feel my situation is very relevant to the OP's.
I have 15 acres of an old farm on which I mow about 3 acres weekly. I had a JD 650 for 15 years w/ a 5 foot mower that I used. Worked well enough, but I really used the tractor more with my implements - bush hog, box scrape, plow, carry all (I bought the whole kit for $5k in 1987 sold for $4.9k in 2003- wish I could buy it back for that). A CUT or SubCut is so useful he will at some point want one unless he just doesn't like yard work.
On the other hand, I bought a ZTR (Toro) after the JD, and my mowing time was cut by 1/2 and the cut quality was just like a golf course. I needed that at the time as I took a job consulting which required a lot of travel so I didn't have much time to spare.
So, my suggestions- get the ZTR now, Cub Cadets do a good job (my neighbor has one he loves) and they're a little less expensive than the big boys (JD, Toro, Kubota, Grasshopper, Bad Boy, etc.) but not as tough. Tractor Supply has them in the $3.5k range right now with decent financing options. It will work for you well for a couple years after which you'll have a better idea what you need on your place. In the meantime, follow TripleR's advice and rent a tractor when you need to.
My two pennies.
Tim