They salt the roads occasionally here and I don't want the rust.
How often should I rinse the frame
it depends how much you drive it , how dirty it gets, the temperature etc...
Just take it through a car wash every once in a while.
and floor of my car?
You probably mean the underbody, and you're not talking about washing the inside of the car where your feet go.
I would suggest you look up your car, and see if it is prone to rusting.
Some cars don't have much issue with salt, others get a taste of it and will rust out from under you.
If yours is prone to rusting, I would suggest getting your frame, and under-body protected from rust. At least it will extend the life of the vehicle. I actually had a friend with a malibu that threw a code today, normally that comes from a leaky gas cap. In her case, rust is eating her fuel filler neck, and caused the leak.
Salt can do nasty stuff to cars, but if you keep ahead of it, you may be able to keep it a long time.
