Has anyone developed or own an online store?

Has anyone developed or own an online store?
The reason for this is just to get the right information...

Let's say I develop an online shopping system or online cart;
What roles does the developer play in this?
I would think that he/she would...

• not need to know the "innerworkings" of each payment gateway available, but know the "innerworkings" of the payment gateway the client needs to use?
• rather suggest an "email system" as apposed to a literal "cart system"? (purely based on the fact that the client would need to pay monthly fees even if they don't make a sale for 6 months)

What roles does the client play in this?
I would think that he/she would...

• need to know the "innerworkings" of the payment gateway they need to use?
• accept the email system, see how things work out, then change to the cart system if needed.

Cheers

I'm currently running an online store for my brother's Ski/Snowboard accessories company.

I thought long and hard about developing it myself but I settled for using a pre-made solution from bigcartel.com. This has worked out well, but I'm looking into something else for this coming up winter.

Having said that, I'm not really sure what it is you are asking? What do you mean by Payment Gateway?

A Payment Gateway is the method of how to get paid.
Here in SA we have two options;

1. You are your own merchant and pay bank fees.
2. You use a company to be your merchant, now you pay them and bank fees.

[EDIT]
bigcartel.com only does paypal no good for SA, even though it was created from someone in SA.
ASP Carts I can develop with no problem, it's the PHP carts that forces me to use Oscommerce and the like.[/EDIT]