lets face it, even with an extreme low sell rate, and a high buy rate from Economics of skyrim(a mod), plus capping speechcraft at 50, i still get a lot of septims from sales, dungeon diving, wife and robbery. I m now sitting with a lot of $$$ which i dont really like.
What mods out there can make you spend a lot of money(e.g. building a town, or funding an expedition etc)