is a post for you. See how you get along with that. As for a pakset, it's a bit different but if more people are interested, I can write a tutorial for that too. I currently play a compiled version I took from Junna, because I've encountered savegame problems in the one I compiled myself.
James: Keeping it simple, yet able to make suburbs cheap vs. expensive city centres. Three (or four) variables, i = city/countryside money distinction (is this really necessary?), j = price of construction on tile, k = neighbouring tiles' construction on tile prices/values (, and l a possibly a passenger success rate based value that would alter the price further upwards). i & j are just called on, but for k; would koord::neighbours and per tile check whether a house/building is present and reading haus_besch_t::price be a possibility? You can then take a fraction of the checked tiles' total prices for the value of k and add that to i + j. Excuse my mediocre grasp of programming.