Agreed, very well under $30k - figure more like the 20's. The biggest things you'll have to contend with, however, is the fact that these are complicated machines. Unlike an e30 M3 which can be taken apart and put back together with basic mechanical skills (one very small and dumb ECU is it for electronics) the e9x platform is riddled with electronics. That factor, crossed with age will mean that maintenance costs are likely to be pretty steep. Conversely, the gas chugging aspect of this car, coupled with the likely pricing in 5 years should also mean you'll get a hell of a deal.
I say, keep reading on the subject so you can be an expert on it and it will make your ownership easy.
best of luck!