The internet has been both a curse and a blessing to high street and mail-order shops. The internet has certainly increased the demand for music, and enabled a lot of people to get access to music they wouldn't normally come across.
Web marketplaces like www.gemm.com, www.netsounds.com, www.musicstack.com combine the databases of many different dealers, shops, mail order companies and collectors to form a single giant database enabling customers to search in one place for that hard to find or deleted music item.
So they get that lost CD and you get access to a worldwide audience, plus there's the ability to get your company’s customer service scored by anyone who buys from you.
The more quick, polite responses you give, gets you more stars in the gallery of retailers, plus most of the markets are free regardless of whether you are a part-time seller with only a handful of items for sale or a large retailer with thousands of items.
On the downside, the internet has also opened up the market for retailers like CD-WOW.com. This site buys the top 100 artists in bulk in the Far East then sell CDs out of large, out-of the way warehouses at £6.99 with next day delivery. This makes the latest Robbie Williams CD selling at £14.99 on the high street look more like a rip-off than value for money.
But if you want to sell on the net then it needn't be expensive. Online catalogue software starts at around £99 and £299, and a website and domain name shouldn't be more than £50 a month. After that, all you'll need is a payment provider like WorldPay to give you some way of taking credit/debit cards, plus credit lines with the usual record distributors and possibly a contract with a good next-day courier.