It costs around $30 per month to build an online store using an ecommerce website builder. You’ll also need to account for your domain name and web hosting, which is included with most ecommerce website builder plans. Costs related to inventory, marketing, storage, and shipping must be budgeted for as well. But your upfront costs to just build and launch the online store today can be done for less than $400.  Follow our step-by-step guide on how to start an online store and make your first sale for more information.