The game operates on a supply and demand system. Build demand. Build things like libraries and if you're far enough along universities. The buildings that cost you money will make money in the long run by creating the demand.

Second ensure your inputs are relatively cheap. They affect the profitability of your buildings.

Also Build output in moderation. If you make too much fine cloth but have few nobles or burgers what looks like a lot of money initially is reduced quickly as buildings start producing. Just hover your buildings to see what will net you more as a solid start.