With the exception of the early (92-94) M42 318, E36s have generally pretty strong powertrains. The documented weak spots are mostly in the M50/M52 six holers; water pump, radiator, fan clutch and VANOS units.
Manual trannys are very strong and will run for a long long time if taken care of. Not sure about autos, though.
All E36s have documented weak spots in the rear suspension. Specifically, the rear toe bushing, subframe mounts and rear shock mounts should be inspected prior to purchase.
But here's a nice thing about the E36. It's fast become a classic BMW. Aftermarket support is very strong on this car and people are keeping them running. So OEM parts are easy to find and fairly priced (about the same as equivalant parts on a typical Japanese import). The weak spots in the rear suspension have "repair and reinforment kits" readily available.
If you have DYI inclinations and are marginally mechanically adept, you should have no trouble wrenching on the car yourself. Or find an indy mechanic who knows the work.
and what about parts affordability in the states?
About the same as a comparable Japanese import. +E36s have been around a long time. +BMW made a lot of them. +People are still keeping them running. = you win.
It's probably a 318i, and an early one, at that. That a good engine?
There is one well known issue with the head/timing case gasket --called a "profile gasket" on 92-94 cars. Short version is the gaskets are defective and are almost guaranteed to fail over time, shooting coolant everywhere. A new part superseded the old part. I would suspect that any '92-94 318 still running today has the new gasket, but you should be careful the car is documented. Otherwise, take $1,500 off the price of the car, no exceptions.
Do a search for "BMW M42 profile gasket" for more info. I don't know of any other weak areas on the M42, though I believe they share the same radiator design as the sixes, so look at that too.
Is it a stick or not? That I'll have to figure out on my own.
IMO, the E36 is really far better suited to the torquey M50/M52 six banger. The M42 was not a bad motor, but doesn't really have the grunt to motivate the 2890 lb. body. With a stick, it can be fun, since the gearing on a 318 is so short it is absurd.
If it is not a stick, I advise you move on until you find one.
E36 318 + auto = tragic fail.
I would think the price difference between a 325 and 318, all else being equal amounts to very little. Maybe a +/- 800 bucks. Not much difference over the time of ownership. And keep in mind you'll probably get that money back when you sell it.
A clean well running '93-95 325is 5-speed w/average mileage can be had in most markets for under $6,000 easy. So unless you find a raging deal on a super clean 318, I don't see why you'd settle for an M42.
EDIT: I've had a '92 325is, '95 M3 Coupe and '98 M3 Sedan. All 5-speeds. They were excellent cars, each and every one. I have nothing but very warm thoughts and good feelings when I think back on E36 ownership. I also had an E30 325e. Many people might disagree, but I think the E36 is simply a superior car in every single way.
M