Don't buy another car unless it is from a friend/family member that can vouch for the condition/history of the vehicle.

If you buy a 10-12 year old car with 120,000+ miles you are taking a huge gamble. Why is someone getting rid of said car? Is it making a weird noise, shifting crappy, leaking fluids? Like others have said, an engine or transmission repair can easily run a couple thousand$.

What you should do imo, once you get online, pick up open time/overtime, and put that extra money towards doubling the amount you pay off every month. It is possible to pay off a good chunk (possibly all) of that $5000 on current first year pay rates. Take good care of your current car and plan to keep it for as many years as you can. Once that loan is paid off, put a car payment's worth of money into a savings account so you can buy the next car outright.

And $1000 for brake repair? Learn to do your own brakes....