My dad bought one years ago and tow it with his corolla minivan whenever he needs it. Chance is that if you only need the bed a couple of times a year or are space constrained you are better of renting it.
I never understood those US mountainbikers who awkwardly wrestle their bike on a truck bed when they could more comfortably mount them on an hitch rack of a regular car or inside a van. VW Multivan must be the most popular van amoung mountainbikers here in europe.