I prefer to use a Gamling Ordinance mod. The 200 a month on the Vanilla game is far far to low imo for a Casino to pay a city monthly for rent and taxes. In reality a Casino can generate millions a year in clear profit, and thats after huge tax and city payments. I think a few extra bucks in SC4 is in order, but not to much. I use the 2k a month version myself.
It keeps you afloat when you need it early game and once the city is actually up and running its barely even noticable in the profit margin.