I want to be able to get power into my house from a portable generator
without the need of extension cords through open doors. I would like
to install an external box that can accept at NEMA-type plug from the
generator and then wire it to a couple of outlets inside the house that
are independent of the rest of the house's electrical system. I won't
need any transfer switch because the power from the generator will
never travel on the main wires in the house.

My question: The box that accepts a NEMA plug has two hot (red and
black) wires. Can I wire an outlet using the red wire and an another
outlet using the black wire (with the white and ground wires common to
both?)

Thanks.