Yep quite often it does mean that selling is their work, you can usually tell if this is so, by exactly what they stock, (click on shop home when you go into the shop) and it will bring up everything they do, some are specialist shops, with web links to their own web sites, others are people who are bulk buying and whamming everything through (who often show as powersellers) so they'll have a bit of everything, quite often you can find out more about the seller by clicking on the me symbol.