Gotta agree with that reply. 6K will buy a lot of good older tractors. Those old Fords and Masseys are classics and will run forever..... but the following 10 to 30 years saw enormous improvements in the utility size tractors - many are available today in that price range.
Those aren't as classic, but they are still from an era that emphasized good long-lasting design for tools of all types.
Instead of Fords built in the early 1950s, take a look at JDs - or any of the major brands - built from the 1970s and 80s. You will get a lot better and more usable tractor for your money.
And here's a hint when buying a used tractor: It should start easily, all the controls should work fine, and it should do some work at 2/3 throttle for half an hour without anything important changing at all. That means no major change to the temperature, pressures, sound, transmission, clutch, brakes, or gauges. And no leaks.
If it will start easy and run like that for half an hour to an hour...., chances are very good that it will do exactly the same for the next ten or 15 years.
er...except during the depth of wintertime.... About half of the good old old tractors need to be warmed up to start well when the temp goes below freezing. There are a variety of block heaters for that purpose. That's not a defect, just as log as it starts well from cold on a summer morning.
luck,
rScotty