Any number of calibers will do just fine for deer. In terms of ammunition sold, the "Big 4", that WalMart has on sale every fall before deer season, are: .30/06 Springfield, .308 Win, .270 Win, & .243 Win. And then there's always the old .30-30 Win if you like the trim little Marlin &/or Winchester saddleguns. You can find ammunition for those 5 calibers anywhere that sells centerfire rifle ammo. Some of these new "short magnum" cartridges & older, foreign rounds may be tough to find at a little country crossroads store.
You might also look at the Winchester Model 70's in a bolt action, before they sell out(been discontinued). But then, I have a soft spot for the good ole M-70 Winchester- mine's a Model 70 Featherweight, Pre-64, .270 Win, bought used with my own $$ way back when I was 16 years old. No, it's not for sale.
If you're buying used, you might want to pay more attention to the rifle than its cartridge. And you can *defintely* save some major $$ with a used rifle/scope combo.
I'd advise against any of the .22 centerfires categorically, & get a .243 or 6mm only if the rifle truly "spoke" to me. Otherwise, anything from 6.5mm(or .264"- more a matter of bullet weights available than caliber) thru the .30 calibers should do quite well for even *big* deer. Though the .25 caliber has its supporters- and the old .250 Savage cartridge is still available, and by all accounts a real sweet shooter for deer. (Way back when, it was also the first commercially loaded cartridge to claim a muzzle velocity of 3000 feet per second- hence its full name, the .250/3000 Savage.)
Repeat- *especially* when buying used, buy the *rifle* first, the cartridge second.
