A player's main source of income is Properties. Income Properties generate the most, but a number of Upgrade Properties also generate income in addition to their main power.
The Extortion Empire HQ upgrade increases all members' property incomes.
When Ariel is in your Inner Circle, your property income is increased.
The money earned from properties is accumulated separate from your cash on hand and money in the bank, and must be collected from the properties page to move it into your cash on hand. The rate at which property money accumulates decreases by 90% when your Max Collection limit is reached. This limit can be increased by upgrading your Safe House.
Cash can also be gained from Bosses, Jobs, Duels, Wars, and Daily Rewards - money from all these sources goes directly into your cash-on-hand.