How do I charge people who what to advertise on my site?

Actually, it is possible to scam. I can tell you how they do it. Next step they either:
a)ask for your personal details (bank account number, etc.) and you can become a victim of an identity fraud.
b)ask for your PP handle and then in a couple of weeks time you get a message from someone who says he's from PP and your account xxx @ xxx.com has been involved in an illegal action and you'd need to give your password.

I know of some guys who have fallen a prey to these scammers.

Please, check the message source to find which country has it been sent from. Then compare it with the whois data of the email address of the sender (the domain after the @ sign). If they match, ask something about their comany and products. If it all sounds reasonable, proceed. Otherwise, ignore them.

And, yeah, the basic idea on prices you can get browsing through DP's section of "Buy, Sell or Trade" where they sell PRx links. These prices are quite accurate, still they are, what I call them, insider prices. So just don't forget to ask a bit more

 

Do'h... what's gone into people. Why the heck people GIVE personal details to some freaking people?

 

I found this topic on google, just to warn you: http://www.f-secure.com/weblog/archives/00001372.html