okay, i have one of the worst conditions e30 around when i got it (dont believe? ask the members here) I spent most of the money changing the worn out parts and repairing what can be repaired. As of today I've spent somewhere in the region of 9K for the car. I got the car for 1K (being abandoned and all).
Now the car is running well, just minor issues with one of the electronic controllers. for the past eight month driving the car, my only expenses is fuel, and regular maintenance (oil, filter yada yada). why dont you check out the e30 maintenance thread for this.
Okay that's over....now I have to warn you, unless you really love the car and are willing to learn and go into trouble for the car, buy something else. The e30 is a very relieble car if it's in good running condition and maintenance is done periodically. if it's not in acceptable running condition, get it repaired. this is where the money flows...repairing the car. spare part are not that expensive, if you know where to get it. Since you are a forrumer, get a knowledgable forummer to help.
Other than that, happy e30 motoring.