It sounds as though you may be looking at setting up a
WordPress multisite network, although some additional customization of the theme itself would be required in terms of having a different homepage from the default listing layout and allowing customers to select from the different stores. But yes, you can disable registration for others meaning only you can place the ads. Please also note that ClassiPress is not an eCommerce theme, so by default there is no shopping cart functionality which allows people to buy from the stores online. Ultimately ClassiPress is not encrypted, so you are free to make whatever changes you like to suit your needs. Thanks.
