Derek wants to create a website for his business and add e-commerce to it. Leo says that's a smart idea. Every business should have a website. It's his digital brochure. Having an e-commerce site is huge because it gives him customers all over the world. And there's a variety of options including Shopify or BigCommerce. They are experts in building online stores. They can also help him with marketing. It's the easiest, but they do charge a fee for it. Yahoo Commerce also does it, but those sites aren't as flexible. If that doesn't matter, then go with it.
If he wants a custom site, then he'll need to go with someone who can design it according to his specific needs. But then he'll have to deal with his own support. Derek should start with one of the services above and then when he's ready to outgrow them into a custom option, he can move on from there. He'll also want to harness social media to help market his site.
Check out the CMO Social Media Handbook by Peter Friedman