Hi Bluegirl and welcome to TE.
A bike can have lots and lots of miles and still be good to go. My husband's road bike is about to be retired as a winter bike and has over 60,000 km on it (roughly 40,000 miles). It needs new wheels and will be a few new parts (again), but otherwise works great.
You can probably just get new, wider tires and an in-depth tune up. You'll be good to go! In the meantime, you can start saving money for your next bike instead of using a credit card to pay for it.
Good luck!