Okay, so as you might have noticed there is one rather large drawback to having a retail online store versus an advertising based / content web business. That drawback is that you need to purchase all the products beforehand. So you might have to spend a couple thousand dollars on products (unless you are making them yourselves or selling information) which puts you in the hole right away (unless you already have a physical store selling those products, then you're just set).
But there is one way around spending your money on purchasing products - drop shipping. With drop shipping you never actually purchase and carry the product. Instead, you make a deal with a wholesaler or distributor that when somebody purchases a product from your web site, you forward the info on to them and they actually ship the product out to the customer (often with a packaging slip customized to your store/brand).
And usually under this arrangement you can get 30 days on the invoice from the dropshipper. So you get paid right away, from the customer who purchased the item(s) from your site, and then you don't have to pay the dropshipper his fee (probably anywhere from 40% - 90% depending on what you're selling) for 30 days or more.
That is not a bad deal at all. So, if you're going to drop ship and open up, say, a Yahoo Store, your total start up cost is $39.95. You can have your own web business for $39.95. Why wouldn't you do this!?
It'll be important to find a reputable drop shipper and one that will work with you to customize your packing slip, etc. But the time it'll take to find one is time spent well.
You can probably find a drop shipper to ship for just about any product line you can think of. Now, let's take a look at shopping cart software.