Check if you need a model release. Photos of people can only be sold for commercial use if they've signed a 'model release' that gives you permission to use their image (children need a parent/guardian to sign). Without a release, these photos can still be sold for editorial use, as long as they were taken in a public place – eg, if you submitted a 'breaking news' shot with people in the background. If there's any doubt, always ask permission.
Provide excellent customer service. Answer any questions buyers post as quickly as possible. Be professional and courteous. Positive communication builds your reputation with buyers and gets you return business. Also, package your product well and ship it out quickly. Allowing an item to become damaged or taking too long to ship can negatively affect your reputation among buyers. Wrap all items, especially fragile ones, in appropriate packaging. Commit to shipping items as soon as you receive payment.
It’s free to join the SellHealth affiliate program, though you do have to apply and be accepted before you can start promoting their products. Once you’re accepted, you’ll have access to a number of tools, graphics, banners and more that you can use to promote SellHealth products. The sales are actually made at company-owned Websites, which look professional and handle all of the selling. Commissions vary, but the base rate is 30% of all sales and upsells, and SellHealth says you can earn up to $350 per sale.