Hi Jacob and welcome to SaleHoo
For the first part of your question, you do not purchase anything upfront with a Drop Shipping business model. You advertise the product, then on the sale of that product, you pass the customer's details onto your supplier for them to process and ship the order direct to your customer. Of course the margin you make is the difference between what the product actually costs you and what the price was that you sold it at.
You can browse through our supplier directory here Link hidden: Login to view. and look for options that best suit your requirements.