those old tractors can do a HELL of a lot of work.... the only advice i can give you, is to check out what spare parts might cost. you can buy some older tractors really cheap... but a simple part like a fuel pump, etc might cost you $1200.00, because theres no aftermarket, and factory parts are long gone.
i picked this little kubota up 3 months ago, by trading a yamaha rhino, and a generator.its a b1750 4x4, its only 20 hp, but its not bad for what im doing, which is mostly mowing in tight places, hauling small trees, and firewood, cleaning up the woods, and moving gravel, and probably a garden. i then put around $2k in parts, iv got about $8k invested in it total, and i just started really using it for my intended jobs at my property a hour away. its small, and easy to transport, but still pretty capable. (tractors are not light.. even my little one, with fel, and finish mower runs around 2000lbs), i love it, it came with a dirt box, and a finish mower, which is actually a really high quality one, and put me about $1800 ahead in implements. i am planning to buy a real bush hog, tiller, disk, grader blade ,logging hitch, and other stuff next summer. its small, but thats not a bad thing, i mowed the other day for 4 hours, and only used about 2 gallons of diesel.
iv used a few older tractors before... and one compact 4x4 john deere...
i CAN tell you that if you do very much at all you will LOVE having a front end loader...... and 4x4 is also very, very nice to have. if you have a small tractor 4x4 is a must have, it triples the work you can do, as in many cases 2 wheel drive will just not cut it with the lighter tractor.