If you're talking about collecting your take or income in the properties, it depends on your class. If you're a 'Maniac' or 'Fearless' type, you don't have to collect anything. It automatically goes...
By mastering jobs and winning fights.
I've just started Mafia wars, but in doing all the street thug jobs, such as corner store hold-up, these cards just keep popping up.
go to properties button and then on the right side just above the list of the properties , there is a button that says "collect take"
you can find cards when doing jobs in new york .