I think you should reinvest your money, once your money has doubled or tripled, I think you can buy a new car!
buying car is not a problem but getting money for taxes, gas fees and maintenace are the thing you need to consider more. dont rush to buy unless you really have enough to cover everything for a year.
How many miles does it have? If it has below 50,000 then you can take it into a bmw dealership for free all the time to get stuff fixed. My BMW has more then 50k miles but has never had any problems.
You could always buy a nice cheaper car.. like a Mazda those are nice... or a Pontiac those arn't bad either...
Try something "viral" such as "HELP ME BUY A BMW". That should help you. Get publicity. Ask people to donate LOL you never know, it could work. Crazy ideas hit a chord with people nowadays.