When first starting out, a business owner may create a website using a template through their webhost and hope for the best. Others will pay thousands to have someone launch and promote their website for them. Although the first strategy is affordable, it is unlikely that the website will generate much traffic outside of the existing customer base. While the second strategy is likely to create new business, the average small business owner probably can't afford these types of rates and will not be able to maintain this approach for long.
There are other alternatives however.
If you are a "do it yourselfer" there is endless amounts of information on the internet. You simply need the time, patience and know-how to use it. You can find information about creating a website with a shopping cart (or you can buy the one that your webhost offers). Basic templates are easy to use. You can read thousands of articles about promoting your website with both onsite and offsite SEO (Search Engine Optimization) techniques. You will find often conflicting, and sometimes completely wrong, "facts" about SEO. Reading the articles, web posts and other sources of information with a critical eye will save you a lot of unnecessary work.
If you are serious about generating income from your small business ecommerce website though, this probably isn't the best use of your time. You should be working on developing your product base and servicing your customers.
As a compromise, you can look for other small business owners who have already taken the time to learn these techniques and have proven their success with their own websites. Offer to barter your products/services for their advice. You will still need to learn a lot about web design and SEO but at least you will have solid information to fall back on.
A final option would be to find a small web design and/or SEO company that is more affordable. While the giant companies that create websites for other huge companies like WalMart would do a fantastic job, you can probably agree that you don't need to invest that much money when you're first starting out. Many small companies just starting out will work harder for you for a lot less money and give you much more personalized service.
Whether you try to go it alone, or hire an affordable consultant to help you out, you can make your small business ecommerce site a success!