After you create a web site, at least a few ok looking pages you can join Linkshare and Commission Junction and start joining many companies that you want to sell their products. Some may want to look at your web site and others will let you start immediately. Pick companies with products that you want to make specialize in. Make a web site focused on a theme that you like and know something about. If you like cars make it about cars, if you like sports or baby products or collectibles, what ever you like make a web site about it and join companies that will have similar products.
It will take time to become popular web site. You will need to market your web site to others, people you know and on the internet. You can buy ads but they are expensive. You may want to spend a little each month to get some traffic. Also trade links with others. make your web site interesting and informative for visitors so they see you as an expert in the field. Link sites of interest and write a little about the products like a review on them. A little time spent each day you can build an online business with your own web site with little cost. The cost would be the price to have a web site. It's not very expensive. This is a good business but takes time to make decent money. The potential is unlimited but it's hard to make large sums of money. It won't cost much but your time and you may enjoy it.