Need to check the laws in your state. In SA, you have to have a license for anything CAPABLE of greater than 10 knots, not just staying under it.
I used to have an inflatable with 4 seats, back to back, forward steering and a 35HP on the back. Probably a bit big to fold up and put in the boot of the car! What it did have though were two wheels fitted onto some 1" square tube held onto the transom (wood) with a couple of wing nuts. Travel along OK with the wheels 'up', then just pull up to the bank, reverse the wheels down under the bottom or the boat, and then just drag the front out of the water and wheel it up the ramp.
Even in a unit, i don't know where you would put even a small boat, motor, fuel tank, life Jackets and all the ather gear required. I suppose it is not a cheap option (depending on what you earn and how much you want a boat), but you could keep it in a self storage shed. Then its just down to the shed, hook on the boat, and away you go.