If you're shopping for a tractor, if you've
never owned a tractor before, and if you're reading the pages of Homestead.org, then I'm going to assume that you're in the market of a
pretty cheap tractor; a VERY used tractor.
This is not such a bad position to be in, because
unlike when you're looking to purchase a car, the mere fact that the
tractor you buy may be older than you are doesn't automatically mean that
you'll wind up with either a museum piece or a pile of junk.
Tractors are tools. They're built like
tools, and the older they are, the more so. In this age when you
have to buy a whole box of screws at your hardware store, just to get the
one you want, you can still buy just the tractor parts that you need
rather than a whole assembly or worse yet, the dreaded rebuild kit.
Not only that, but in my state, you don't even have to pay sales tax on
tractor parts.

In fact, you'll find that as often as not, quite a few of
your tractor repair parts might even be considered
cheap. After all, they've been making head-bolts for your 9N
for the last 58 years. If you harbor a few vague notions about how
the internal
combustion engine works, you can probably fix your tractor yourself with simple
hand tools.
Try that with a new car.
Probably
the preeminent cheap-and-easy-to-repair older tractor is the Ford
9N-2N-8N series (see top of the page photo) but you can also still find parts
readily available for other older-model domestic makes such as Case,
International-Harvester, Massey-Ferguson, John Deere, Oliver and Allis-Chalmers, although you'll probably be dealing with differently-named
companies. (John Deere is the only one of those mentioned doing
business under the same name.)
So relax, you don't have to be a mechanical engineer to
buy a used tractor, you just need to know what you want to do with your
new-old machine and look for a few particular things.