Wind, The literal meaning of "to have your money tied up in futures" means "to have your money promised to pay future contracts." --Penny has a lot of her money tied up in promiscuity futures.-- This is only a play on words and does not have the literal meaning of "tied up in futures". It means rather that Penny is spending her money on promiscuity now with hope of a future gain. This gain would most likey be a future husband. If you would include more context in your questions they would we easier to answer. I searched for the episode that you quoted from and you can see from the context that Penny is indeed hoping through promiscuity to gain something. I hope she is looking for a mate, but perhaps she is just being promiscuous for the free drinks. :) What do you think? ==== “Let me ask you, when you get back out there, are you wearing this?” – Mrs. Cooper “Look, it’s super cute on. That top has paid for itself in free drinks like ten times what it cost.” – Penny “Yes, Penny has a lot of money tied up in promiscuity futures.” – Sheldon “Hun, do you think maybe the reason you’re having trouble finding a guy to settle down with is because you’re letting him ride the roller coaster without buying a ticket?” – Mrs. Cooper “Oh, they don’t always get to ride to roller coaster. Sometimes they only get to spin the teacups.” – Penny

The context seems strange. Normally, when money is "tied up", it is invested and not liquid. If my money were invested in real estate, I would say it was tied up in real estate. I think the statement is a joke, a play on words, along the lines you suggested, namely she expects a return through sex.

tied up = invested