I've been going through the Far Horizon Core book, but I'm not seeing how to calculate the monthly profit of the business/homestead. Is it just taking the monthly salary from the jobs table? Or is there something more to it than that?

The base profit is zero...basically the homestead makes enough to cover expenses but not more. If you want a profit, you need to upgrade it.

The top section of the tables on pages 83 and 85 show the monthly profits per party member.

A homestead is 100/per PC x # of upgrades (5 being max)

The business is the same formula, but 200/per pc