A Kia with manual transmission is towable 4 down with no speed or mile restrictions. If you want to do it that way, you'll need a base plate that fastens to the car's undercarriage and allows connection to a tow bar. You'll also need a braking system so the car doesn't extend RV's stopping distance. If you buy new and have it installed, it'll be something probably over $3000, including wiring for lights, base plate, tow bar, braking system.
If you do it yourself and buy some equipment used from Craig's List or the like you can reduce costs by more than half the above.
A new tow dolly with hydraulic disk brakes would be around $1800 new, but you can find them used. A tow dolly is a little bit more time in running car up on the dolly, fastening down, storage of the dolly when not using, etc, BUT it works for many cars and doesn't limit you to the customized Kia Soul you'd have doing it the tow bar way.