Well as far as costs go you areprobably looking at between £50-£100/year for hosting max!
If you need someone to design a template there are some good designers laready who post on here, I am sure they will pop along if you ask
Very reasonable prices too. Nick and Dezina can help with banners etc and templates
You can use a free shopping cart like zencart too, or you have cash to spare there are some very good ones around, i am sure some memebers on here have some, openmind I think is one??
So costs to start with are minimal. Then it is the SEO to work on etc but lots of useful tips on here and there is always someone who can help if you get stuck.