Film goes bad, especially if stored in warmer temperatures. If someone has been keeping the film in the fridge or colder, it can stay good well past the expiration (years past) so expired film isn't all that bad. If you're not doing anything important you can try out a roll and see if it is OK and then go back and buy more from the same person or store.
Expired film can also be very interesting with the color shifts it can produce.
You can get in to black and white processing really cheaply these days with Craigslist; I've seen full darkrooms (enlarger, trays, cans, reels, chemicals) going for $35. Then your only expense would be film and paper, not developing or prints. Color slide processing isn't that much different from b/w negatives, just more sensitive to the temperature.