Overhead cost of an Ecommerce web site is generally much less than the cost of a physical storefront.
You have the ability to reach customers all over the world rather than being limited to a certain geographical location.

Customer Benefits:
> Order your products without leaving their home
> Security knowing every transaction is secure.
> Purchases will be delivered directly to their door.
> Search and find what they are looking for instantly.
> Viewing any or all of your product specifications and photographs
> Choosing from a variety of options such as size and color
> Checking how much they have "spent" before committing to a purchase
> Contact you for customer service

That depends on how complicated the site will be. It's possible to have one up and running in two to three weeks.

The most common methods are using a simple online order form, or a shopping cart system with an order form. Once your customer completes your online order form the order can be delivered to you via email, saved to a text file or saved to a database file on your web site for you to retrieve.

Upon receipt of your customer's order you can submit their credit card and payment information to your merchant account provider and deliver your product or service.

That depends on how complicated the site will be. It's possible to have one up and running in two to three weeks.