Well I was kinda hoping to just draw the blocks, just smooth abstract shapes, a lot faster than making individual buildings.
Of course important buildings will be drawn differently to seperate them.

I think what I'll do is make simple rectangular shapes copy pasted for the individual slum buildings, no detail, any part of the slum that's a bit denser will be connected shapes.

I mean, i'd love to have detail on the buildings, but it would take me forever to do, and the result would be very busy looking.

It's still up in the air, so i'll have to think on it for a while.