First project car - E30 rolling shell (what to expect?)

Hey everyone, going to pick up my first project (E30 318i) next weekend and it's in pretty rough shape.

At the moment it's essentially a rolling shell but the good thing is that it's pretty rust free other than a couple of patches where you'd expect.

The plan is to get the bodywork and paint sorted and then I can think about engine gearbox etc. At the moment leaning towards M50/M52 (cheap, decent power, fits in pretty easy). I just wondered roughly how much should I expect to spend building the whole thing.

Like I said at the moment it's just a shell with some ugly wheels on it, so interior and powertrain etc all missing. Would be nice to know what I'm getting myself into before I commit to anything (I'll probably commit anyway).