Is there such a thing as a portable, affordable, two-way radio system
with 10 mile coverage or better?

What about something that is slightly secure?

Here's the need that is driving this:

I can't really afford cell phone bills. I live near 5 families of
relatives in South Carolina USA, each within 1 mile of me. Each
morning and evening, I travel a long 40 mile road with no cell phone
tower in sight -- zero coverage, even if I bought a cellphone. I would
love to have a device that each of us keep in our cars, always turned
on, as well as in our homes, and it would only provide communication
among myself and my relatives. I would prefer to have something that
could not be eavesdropped very easily, but I would take whatever I
could get.

BTW, I don't know much about HAM radio, so please forgive my
ignorance.