For the past two years, I’ve used print-on-demand technology to create and sell products in my e-commerce store. Though it’s been fun selling mugs and tee-shirts, it’s also a very saturated market.

If you've seen an online ad for it, it's possible Rachel Rofé has tried to sell it. Since 1997, Rofé has dabbled with ways to make money online. Her early days consisted of scouring thrift shops for ...