I would have to say that everyone so far has given you great info. There are so many good GT's you can still find parts for. I wouldn't be afraid of any of these brands, each have there good and bad points. If you are a decent mechanic, I wouldn't be afraid of any of them. Several of these brands offered Diesel models also.
Any of these can be picked up with attachments for less than 1,200.00
This is just my opinion and I wish you the best of lick finding something to fit your needs.
Texas hit the nail pretty well. I am personally a Sears fan, but I also have a MF 1855 I have yet to even drive. I got a killer deal on it, so I thought, after I got home, starter came lose which requires motor to be removed upon I discover carrier bearing on driveshaft and ujoint locked up....i.e. custom driveshaft...i.e. mucho $$$$$ I bought it in July, still have yet to get it back together.
I have 3 sears, I work the dog poop outta my 1977 16/6 single. I custom made from winch and snow blade and dump bucket, but I have 3 point with disc, plow and will may rear grader blade. It does everything I ask. I can run a 3 point tiller with a separate motor also if I wanted, but I have a troybilt so no need at this time. I do like the Masey though, the hydro foot control is great over shifting. I'm not a JD fan, but the 318 seems to be about the best well rounded tractor, has hyrdualic controls and ports to add equipiment, but IMO, they are overpriced, at least for my budget.
The best advice is tough, search CL, if ya see something that might fit the bill, ask and reearch that model. There are enough experts that can give you sound advice. You too will have to remember, your price range puts you into an older used tractor, repairs are expected.
The sears 18 in the for sale section is a decent tractor. Not sure how easy to find 3 point lift for rear, but it's a good starter.
Here is my sears working. ( we all like tractor porn no matter make/model )