That depends on what you want to do and how you want to do it. Basic storefronts Enabling your Web site for e-commerce has never been simpler. If you have average or below-average computer literacy, you should find a vendor to host and maintain your storefront. Depending on the number of items you have to sell and the complexity of your site, a good vendor can get it up and running in a weekend, if not by Saturday night. If you're up to it, you can probably set it up in a weekend, if not by Saturday afternoon.
Some software is shareware and can be downloaded and tried for free.
But make sure you weigh the ramifications of setting up your own e-commerce site. Secured servers, merchant accounts for accepting credit cards, inventory control, and summary reporting are just a few of the headaches you'll face. These can be used to at least provide a catalog of your offerings. When users want to buy, they contact the site and arrange for payment using whatever method the business and the customer can arrange. If all you're contemplating is setting up an online catalog, you can be up and running your storefront in a weekend, if not by Saturday morning.