jjnz1: I did some reading before I carefully wrote the OP. I am not selling, only sharing and as far as I can tell sharing is not explicitly mentioned in the T&Cs.
If money is changing hands between you and someone using the wifi network, you are selling. Have you spoken with your ISP and asked them if they are happy with what you are doing?? Somehow I don't think so.
To me it's like driving around without a seat-belt as you don't seem to fully understand the legal implications of what you are doing. I'm sure people could drive around for years not wearing one and be fine until the time you needed it and you weren't wearing it..... and quite possibly from no fault of your own.
Beware there be dragons.... Never let it be said you weren't warned.