My daily driver for the last two years is a 20 yr old sport(y) car ('88 Mitsubishi Starion), so of course I think it's fine to get an older car. Just be sure that:
- No rust/ crashes
- No signs of it having been dogged or abused by a teenager or somethin'
- The lower the mileage, the better of course.
You should be able to find something meeting those requirements for waay under 8 grand.
Of course once you have your car, you will have to be sure and keep on top of preventative maintenance a lot more than with a newer car. Above and beyond the normal tune up, you should do stuff like replace all the fluids- including brake, clutch/transmission, and flush the radiator fluid, be sure all the suspension points are lubed, go through your electrical connections w/ some dielectric grease, replace old crusty belts and hoses (including vacuum hoses), etc...
And if/when you do have problems w/ it, I suggest you find an online forum specific to your car (just about every cool car has one). They'll be able to help you out w/ problems much more specifically than a general forum like this one, plus it's a good place to make connections for cheap OEM replacement parts.