Selling patterns you've scanned would be copyright infringement, so that's a no. Unless the copyright has expired, but they would have to be very old patterns.
Yes, I've seen patterns from the 70's scanned and posted here, but if the seller was caught they could be in a huge legal mess.
Heck, I've even seen people take free patterns they've found on the net and sell them online. I saw a seller once remove her illegally listed patterns when contacted by the copyright holder, only to put them right back up a few weeks later. I mean...HUH??? I think the second warning was probably a little more strongly worded, cause to this day, I don't think the seller has put them back up for sale.
What you can do is sell the actual original pattern, there is nothing wrong with that.