The one downfall to BMW's in the US, they aren't at all cheap on parts. About the only parts I know of that are cheap are probably the brake pads and rotors. Spectre pretty much hit the nail on the head with 'em.
I'd say if your unwilling or unable to work on the car yourself, to pass on the bmw, or hang on to some of that 25k you'd have spare to do any work on the car.
I don't think the e36's have all that many problems though, the M42 has a timing chain tensioner that needs replacing every 70k miles (but BMW doesn't state that), and it's oil pan bolts like to back out and drop in the pan. Both are very easy to prevent/maintain. The tensioner is a 2 minute job and requires a 12mm wrench. The pan bolts just need to be retorqued once in a great while.
BMW dealer labor costs are about $100/hour, but dealers are some of the worst places to go to have your car worked on IMO. Take it to a specialists shop instead, probably cheaper, and will be more willing to use aftermarket parts. And are less likely to rape you on parts costs than the dealers (though not always).
And I am forgetting, SoCal has a severe lack of Low mileage E36's, as you'll find out, it's hard getting around with out putting a lot of miles on a car there. You do have the benefit of a large enthusiasts following. SoCal was the place most imports were sold in the US for a long time, especially old Japanese tin. Then you get all the yuppies that had to have the benz's and bmws.
I'm putting in a lot of effort on this and I know I shouldn't.
www.autotrader.com is the common place to look for cars.
If you want to find a rather good deal though, look in the local papers, especially the OC register and whatever the Riverside county one is called (brain is failing me ATM). For some reason people forget that cars are posted in the papers and owners don't get a lot of calls on them. Also the Recycler is a great paper as well. Usually coasts about $1.50 and are at most grocery stores and gas stations.