Regarding an e-commerce site, do you mean the developer costs of building/maintaining, or the hosting costs?
Most hosts are able to support an e-commerce site though your best choice will depend on the system you intend to use. 'E-commerce enabled' could mean anything from adding Paypal buttons to a static page through to an advanced system like Magento.
Once you know which system you are going to use, I tend to recommend contacting a shortlist of hosting companies by email to ask if their package would support that system. It'll give you a feel for how quickly they respond to emails and whether they are able to talk non-techie!
the chap who manages my site is Simon of UKSiteBuilder - he know me by this name - and I'm very happy with the support and service. He could give you an idea of costs and levels of service - the more you do yourself, the less it costs
We would recommend Media Temple and it would cost you $20 per month for your website and email to be hosted. Their support is excellent. I would steer clear of 1and1 they are cheap but their support is awful!
Let me know if you are interested in a web designer. I can do everything for you - design your logo, setup hosting, email, design your site, integrate you with social media. I can do simple marketing sites or e-commerce with quick and easy instructions for updating and making changes to your own site. Please mail me directly if you are interested.
Hosting depends on what software you will use. We are a WordPress training company so if you plan to use WordPress for your website we would recommend either Heart Internet - www.heartinternet.co.uk or WPEngine - wpengine.com, depending on your budget.
We have helped over 3,000 people create their own websites and have chosen these suggestions based on all their feedback!