Command-R (booting to a Recovery system partition) does not exist before Lion, and would not do anything on a Mac that has never had Lion or newer installed.
The cheapest way to proceed with a reinstall of Snow Leopard is to purchase the installer DVD direct from Apple. You have to call 1-800-MY-APPLE (800-692-7753), and ask for a sales rep, who will sell you a copy, with free shipping to you, for $29. Snow Leopard is no longer available for sale at an Apple Store, or online. You have to call them, and order it over the phone.