I have received numerous emails advising that I have money in my paypal account from sales and ones that also say invoice from paypal that I need to pay. The problem is I haven't been buying on line for a while except through trusted sites that I have used before. And have not bought anything on Ebay in a long time. These are all fake/fraudulent attempts to get money from you.
Even with echecks, they could have something set up that shows the funds available to you they can use a pyramid type system to cover the check but then somewhere down the line they pull the funds and then everything collapses and people get ripped off. So be very careful who you deal with.