, Proton2 wrote

The problem with getting a credit is then the user has to be charged, otherwise you might be the one using it to get credit for your own use of it.

Once you start charging a user for using it, they might as well have stayed on the regular cell network.

both parties contract with a broker. People with WiFi capacity sell that capacity to the broker. The broker supplies the customized dd-wrt software to run on the wifi router. Buyers, who want a wifi connection, pay the broker per month. The broker supplies the software that runs on the PC or handheld device that enables it to connect to the wifi of those who are selling their capacity.