Good luck, as you have learned, there is generally no "cheap" way to do this sort of thing, just "less costly". I too am an older guy. I grew up farming and then got out of it to the point I didn't have any kind of tractor. I started by using my pickup then ATV then a well used Ford NAA.
I now have some fairly new equipment and the work is much easier. I know from experience that you don't get younger or stronger with the passage of time, so be thinking long term even if you can't swing it now. As per Soundguy older tractors are still a pretty good way to go and if you are mechanically inclined. you may never need anything else.
In the interim look at a good spray rig for weed and sapling control and maybe some controlled burns.
Good luck.