1. How do I know Project Payday isn't a scam?

Project Payday existed since 2006 -- and so far, they haven't shut down yet. But they shouldn't, because it is a legit way to make money. Basically, you sign up for products, test it, and cancel before the trial period ends. (to avoid getting charged on your Visa). You can collect cash, computer monitors, ipods, whatever. But I recommend getting cash ought. :)

2. How much am I expected to make?

You can make anywhere from $500 to $2000 a month, working part-time at home using your computer if you're willing to put a couple hours working. If that sounds like something that you could do, then the Project Payday program is for you. 

3. Do I have to invest anymore money into Project Payday?

No. To get full membership at Project Payday, you have to fill out some surveys in order to join for free. If you're feeling lazy and don't want to fill out any surveys, then fork over $30 to instant access their membership area. Whatever you do is up to you.