Is a website that lets people list their unwanted gift cards for sale a good idea?

I want to know if this idea could make me a lot of money. To make money on the site, I would charge the seller a small fee once the card was sold on the site. I would also put advertisements up on the site and a subscriber newsletter that could promote affiliate products. If you don't think this online marketplace for gift cards idea is any good, please tell me how to make A LOT of money online and some of the best online business ideas to try out that could be profitable.