While you may be ok, I'd like to throw out a warning:
DO NOT TRY AND GO CHEAP ON A RIG!
particularly the suction cups and their connection to the tubing. I know of multiple people who have dropped their cameras.
That being said... automotiverigs [dot] com from back in the day was wayyy overpriced.
Do your research and build the setup that is best for you.
Remember that if you shoot during the day you will need a neutral density filter or some way to stop down the exposure(sometimes just a CP is fine)
Also, if you try and make a rig longer than 10' or so it gets real tricky to keep it steady.
Do realize you need a wide angle to get those types of shots.
Now, when it comes to taking the shots:
-Exposures are generally long (at least 1 full second)
-Speeds are very slow(<5mph)
-Often you may choose to roll the car without the engine on to reduce vibration
-Watch your surface that the car is rolling on, don't expect a shot with a 20' pole to be steady on a gravel road!!
If you are curious how these shots are done on an epic scale... check out this vid: