Love, live, and can't find enough time to kayak...whitewater and sea.
I use Yakima products.
But if you are not hauling a long boat (even if you are...say up to 12 feet) or going a great distance, you may get by with just the foam pads on the roof.
Use a tie down in front and back. Don't over tightened to the point of causing bending in the boat (very easy with the plastic one). Just tight enough to hold it in place.
Strap side to side with a rachet type strap (self tightening...not one of the "come along" types) will work usually with the doors closed.
This is ideal for short hauls and short boats. Done it on every thing from my volvo s60 to friends honda civic to a mazda 323.
If you're doing this for a distance drive and plan on doing it much, it pays to invest in a good rack system. One that will stand the kayak on its side is best. The material used today can get distorted and mis-shapen in the heat and tied/strapped down too tight when the hull is used as the point on the rack.
Yakima is great products with many made specifically for this sport.
If you plan to go the Yakima route, PM me. When I get home from work I will send a site to you (if I can find it) that has the absolute cheapest prices. If I have it and it is not being used, it will even be cheaper.
By the way, no boats for sale. Did sell the whitewater (Dagger) due to vertigo...kind of freaky feeling when that hits. At one point we had 9 (wife kayaks also). Still have 5, mostly touring but a couple creeking/river runners.