I agree with
@pdqdl about a 40-50HP tractor...but not necessarily the mower. How often do you want to mow and how nice do you want the grass to look? My shop is on 5 acres of an old golf course. I was conflicted about what to do with the grass. I just bought the land and was paying for a building. I don't really care about the grass, so I while I was looking a lot at 6' ZTRs, I couldn't pull the trigger on a $5-6K mower. I rented a tractor a 7' bush hog once. Worked great, but too costly to be a long-term solution.
My answer came when a neighbor asked if he could store his 35HP tractor with a 6' bush hog in exchange for letting me use it. DEAL! No, it is not as fast as a ZTR. No, it doesn't give a good "finish" cut, but it knocks the grass down.
Another neighbor has a Grasshopper ZTR that he is going to get rid of and put a finish mower on his tractor (don't know the model, but it is decent size - probably in the 50HP range). Says the ZTR is too bumpy (again, this is an old golf course, not a recently cleared woods).
I also have the old 12' reel mowers that got left when the golf course closed. They do OK now, but I have high expectations for those once I get them cleaned up and sharpened (in my spare time...did I mention I don't care that much about grass - so there isn't a lot of interest in making time to work on those LOL). I'd recommend seeing if you can find a set to pull if your property is conducive to those. Pretty sure at 2x the width of a ZTR, this will give me less mowing time even using a slower/less maneuverable (compared to ZTR) tractor.
OK...back to you getting a 40-50HP tractor. Your needs:
1. Had to cut grass. I dont need something to make my yard look like a golf course but it does need to cut as I don’t have room to store two “tractors”.
Check...you can choose: bush hog, finish mower, reel mower...
2. Needs to be able to have enough oomph to haul trees out of the woods and up a slight grade.
How big are the trees? I'd rather a tractor on a slope than a skid loader all day, every day...but I'm not an expert skid loader operator. Maybe get modest sized trees on pallet forks. With a log arch, you can pull pretty decent sized trees. If you have several big trees, is it worth having a commercial logger take them? 4 acres isn't much, but if you have 50-60 trees that are 18" diameter and bigger somebody would buy them around here...
3. 4wd would be a bonus.
A bonus they'll gladly let you pay for
4. If I’m going to get one I’d like to be able to plow my driveway - hoping I could use the existing bucket to do so.
Front end loader bucket would be one option...blade on the back would be better for $600-$800
5 as a bonus ability to attach a backhoe would be appreciated.
Many can put on on the back powered by PTO. But I agree that if you are only going to use it a couple times per year, renting a mini-ex may be a better answer.