This opportunity comes through affiliate programs that pay you to send customers and sometimes even visitors from your website to the advertiser's web site. The merchant pays you for the customer, either as a percentage of what they buy or a simple fee for sending a visitor their way. You never have to take the orders directly or ship any merchandise. That's taken care of by the merchant. You just operate your website.
Some merchants run their own affiliate programs, but very few anymore.
The admisinstrative process of dealing with thousands of small to medium size webmasters is not their core business. Most have outsourced that that function to companies who specialize in running affiliate programs and helping the affiliates become successful. The outstanding leader in this industry is Commission Junction. Commission Junction runs affiliate programs for an ever expanding clientele of merchants that now number over 1,500. As an affiliate of Commission Junction, you get to look at the affiliate program offerings of all 1,500 merchants and apply for the ones you want to include on your web site.