I'm trying to figure out the same thing, and I'm a novice programmer. I work for a non profit having nothing to do with computers and being a novice here makes me an expert there, and our budget isn't ready to support hiring a pro. I'm looking for some open source code that can do this, but for now, I have a $1.00 product and ask users to get, say, 50 of them to make a $50 donation.
Not slick, but it works.