I think fastcommerce sounds like a scam to me.. Just my opinion, but any store that limits you to the number of products and all that also is going to limit you in a lot of other things..I mean, to have to PAY per month just to use paypal checkout and google checkout, which are free services is crazyness!
On the other hand, you can opt for zen cart.. Zen cart is an offshoot of oscommerce, and it looks a little prettier out of the box. They have installable templates that will get you started and best of all ITS ENTIRELY FREE!!!
Then all you need is a hosting account that will run you around $7 a month ( i have a link to a good one if oyu want it, PM me) You can then choose a regular paypal account, or a paypal pro account where the customers never leave your site (like a merchant account on the bigger websites) You can also just get yourself a merchant account if you want, i just suggest paypal pro for beginners.