I have 2 level 4 nightclubs, they pay out almost 2 million every 6 hours, they are very expensive to upgrade and they get robbed probably more then any other building I have, and I'm at over 1.5 mill per hour...

But then again, even after being robbed I'm pulling in a lot of money, seems silly to me to not build something just because it might get robbed.

I'm currently working on upgrading the next one to level 5 once my loft finishes upgrading to level 10, it's at 8 right now

But all in all for IPH they are the best for your money.