Don't mind me...I am going to type out loud for a min here...
It is a little harder then it seems...you can purchase a shopping cart script pre-built and then try and fit into the website...it never looks right. So best off creating a custom one...and managing a backend for inventory...
Then you need a website to put it in...could use wordpress...php is good for this...however you'll have to purchase an SSL for secure transactions or nobody will ever buy from your site. And I am assuming that you want the site to have a professional look and feel? So we are talking custom templates.
Then you'll have to setup a merchant account with PayPal or one with someone else to process credit cards...then you are paying a fee on every transaction to do so.
You are looking in the ballpark of $1,000 to $1,500 to do this job. ..well if I did it at least...probably one of the lowest quotes you'll get for it. Also, would take a lot of time to complete.
And you still have to purchase a domain name and order hosting and don't forget to purchase the SSL and set that up.
You can probably get lower quotes out there...but I can't guarantee what the site will look like