If you install LinSpot on your AirPort equipped network, it will turn that into a hotspot.
Customers who drive by or your neighbors can connect to the Internet for a low fee.
And that fee goes to you!
You can still give unlimited free access to your friends. All online payments are handled through PayPal and processed through secure end-to-end encryption.
In fact, it works with any WiFi router and even behind a Firewall doing Network Address Translation (NAT) and it auto-configures itself.