Normally, with a trade port, the payment for your wares shows up all few days when they sell.
With gambling however, this is different. There is no direct payout as far as I can see and it is also not in the budget window at all.
When I look at a Casino or Gambling House, it tells me what I earn per day but also what I pay or earn per hour.
So when does the game exactly take away or add the money I lose or make via gambling?