For the past seven years, I've made money off of every online purchase I've made. It wasn't because I'm incredibly talented at finding coupon codes, patient enough to wait for sales or secretly running an eBay business in my home. It was because I've been taking advantage of cash-back shopping, and often combined those savings with sales and coupons.

How Much is 30 Seconds of Your Time Worth?

The secret to capturing hundreds of dollars of free money is by simply adding one small step to your online shopping process. Instead of going directly to a store's site to purchase an item, go to a cash-back portal like Mr. Rebates, Ebates,ShopAtHome or FatWallet and click through to your desired store through these sites. That small step, which adds 30 seconds at most, can earn you 1 percent to 30 percent off your purchases as cash back. For example, of the writing of this article, Mr. Rebates was offering the following cash-back rebates: 6 percent for Nordstrom (JWN), 6 percent for Banana Republic (GPS) and 5 percent for Nike (NKE).

Cash-back portals have affiliate relationships with the stores listed on their sites. Each time a cash-back portal refers a paying customer to a store, it receives commission, typically a percentage of the sale. In return for you going through their portals to do online shopping, you share in this commission. This revenue sharing has allowed me to make more than $700 just by adding one small step to my shopping routine.

Sales, Coupon Codes, Credit Card Rewards, Bonuses (Phew!)

In addition to getting the cash back, these portals also aggregate coupon codes by store, which saves you time and hassle. Best of all, this cash-back benefit can generally be combined with existing sales, coupon codes and credit card rewards

Read more: One Easy Way to Make Free Money While Shopping Online