Sharing Wireless Highspeed

Situation:
3 Family members live in a Rural area 'Valley', and are unable to get Highspeed other than Satellite which is worthless.

1 Family member lives on a Hill overlooking the valley, and they are able to get Wireless Highspeed from a local provider.

What are the rules about building a wireless network linking the members in the valley with Point to Multipoint wireless Equipment to the person on the Hill's Highspeed access, and then they share the bill?

Is this like stealing Cable in the old days? Can you steal Bandwidth?

I don't know if the ISP charges by the amount used, or just unlimited.

At this point in time, sharing your back-end internet connection is only a violation of your ISP's TOS.

But with corporations having wet dreams of misrepresenting your physical description on a social networking site considered illegal access to a computer network being a Federal crime...who knows where it could lead.

If you did this your ISP could not or not...