How to make more money?

Money income is based on the number and levels of the banks (but limited by the amount of population you have, check the money tab for the Efficiency which will be below 100% if you don't have enough population.) Level up banks to earn more.

You can increase this basic income by recruiting and stationing certain heroes in the banks and unlocking their skills that add to the income. For example the 'Resistance Leader' Hero will have bank improvements skills.

Class also matters. Raiders have 30% lower money production, but can raid money from others using the class APC. Farmers have normal money production (+ a depot protection), Traders earn 50% more money which is good but have no protection if they are raided.