It's a common question, to give any helpful answer we need to know what the land is like and how you are with mechanical things. Experience and tools? Just want to learn? Have you built houses and barns before?
Not being nosey, its just that the answer as to which tractor depends on more than the tractor.
In the meanwhile, here are some hints...
10K will buy a nice used car, but not much of a tractor. 20K will buy a nice used older tractor.
A used tractor is all about condition. They are so rugged that age doesn't much matter. A good used old one can last forever, an newer abused one is a money pit.
You probably are wasting your time looking online to buy a tractor. Online is good for education, but not for buying. To look to buy, look locally. Get out and talk to people. Ask in feed stores instead of tractor dealerships. Ask at local farms, find who maintains the county fair grounds, ask at small town road & maintenance departments. Go back to that feed store & ask if they have a bulletin board. Get a copy of the local farm newspaper - farmers still use them. Avoid auctions absolutely. Never buy anything there.
Yes, after you get above 50 hp, 2wd tractors will do what you are looking to do just fine. Also, it doesn't have to be diesel. Old gassers work too. It would be nice to have a FEL and a heavy blade on the back. Anything with a FEL must have power steering.
The main problem with really good older tractors is that people tend to keep them rather than sell them. Oldsters find it is easier to just keep an extra old tractor than it is to be constantly changing implements. Those you only find by talking to people who have them.
Luck, rScotty