One of the biggest advantages for doing business on the internet is the low or no cost that is involved in starting and managing the business.  Take the place where you do business; which is your site, your online store.  Most sites can be setup for free by a hosting company.  You can either design it yourself or have someone design it for you, again for free. 

Products for your business can be obtained for free from various affiliate programs.  You do not have to pay for storage of the product because this is done for you by the actual seller — you are just the commissioned affiliate.  Once the prospect lands on the sales page and makes a purchase, the seller will process payments, pack and ship the merchandise for you.  Again, for free.  And you are paid a commission on the sale just for leading the prospect to the landing page through your promotions.

Now, some promotions you run can also be free.  For instance, you can write articles with links to your site, about the products, and have them published on hundreds of directories on the internet for free.  The articles act as advertisement and through the links will take the prospect to your site where you, in turn, through links or banners direct the prospect to the sellers landing page — where the sale is made.  You can also get prospects to your page through links with other web pages or through your position in search engines.  All again for free! But keep in mind that paid advertising such as solo ads will bring you better results.