How old do baseball cards have to be to be worth money? :)

There is no set time frame for a card to appreciate in value. Generally, the more rare the card, the more it is worth. However, what the player accomplished for his career, who made the card, the number in circulation, the quality of the manufactuer, demand by the consumer, etc. all go into what the card is worth. I have seen cards plummet in value because of e-bay and the steroids scandal. Cards are not worth as much as 10, 15, 20 years ago. I should have sold my Jose Canseco rookie card long ago. My Cal Ripken Jr. rookie card (Topps 1983 ) was once worth $60 ( late '80s, early '90's ) and now it is nowhere near that. I think the market is weak, but like everything, it should cycle around and become strong again in time. Hopefully, in my lifetime.