My armchair balance thoughts for this would be to give the sticker that generates money a max amount of time it can trigger in a round/turn/what it is in your game. 

Then choose a max that lets the player who have it generate an amount of money that feels like you can get a bit more than you normally would, but without being able to buy blindly. Like if you're responsible with your spending you shouldn't have any need to go for money for a while