As far as older farm tractors go, the Ford 2,8 and 9N's are usually in a decent price range, but if you get one make sure it either has liquid ballast or get some for it. They are very light tractors and need as much traction as possible. I suggest Rim-Guard if you can get it. The Massey TO-30 is basically the same tractor with a Contenential engine. Some of the older Massey-Harris stuff can be had on the cheap and are decent machines. As far as the Cockshutt stuff, if you can find them, parts are getting hard to find for the Cockshutt made tractors, after 1961 they were mostly Olivers painted Vermillion red and Cream, with one model being built by Minneapolis-Moline and I think is the same as a Jetstar 3. You might find some older Olivers in that range, 60, 70, 66, 77, 660, 770, and some of the small utility machines built by Fiat.
IH's, if it has Fast Hitch pass it up, they can be a nightmare to hook up to Fast Hitch implements. Their cast iron sucked too, really weak and of poor quality in general. Good runners though. JD, well......I doubt you will find many under 1000$. If you do it's probably going to be a 2 cylinder, nuff said.
Allis-Chalmers WD's can be low cost and there is a ton of parts out there for them. They will out pull a 8N by quite a margin. The Snap-Coupler hitch can be a little tricky, but not the task that Fast Hitch is. Most of the mentioned brands are now owned by AGCO, Allis-Chalmers, Oliver, Minneapolis-Moline, Cockshutt, White, Massey-Ferguson/Harrison, so parts could be bought through your local AGCO dealer.
Good luck with your purchase, JJuday