I don’t know much about it, but I have heard that there are many kollel people in Lakewood and Flatbush that make extra money by selling stuff on Amazon. You can’t do it properly without learning how, so don’t just jump in and try it out before someone teaches you. But I think it works something like this:
Every item for sale on Amazon has a seller rating, which indicates how popular it is and how quickly/guaranteed it is to get sold if you tried to sell one.
These entrepreneurs look for very hot selling items. Then they look to see if they can buy it elsewhere any cheaper, such as on sale in Best Buy or Staples, or with a coupon, etc… Sometimes they even pay the same price, but use Credit Cards or ebates or other reward programs that earn them money or mileage for each purchase.
They sometimes might have the item delivered straight to Amazon’s warehouse from the place they bought it from.
I think one of my neighbors is doing this, because he frequently gets UPS deliveries AND pickups of a lot of large boxes.
Items might be toys, computers, or almost anything.
Hatzlocha!
BTW – App Development is a good legitimate business, but it probably requires certain skills. It might not be for just anyone.