I have a yakima bike rack that mounts to te trailer hitch. hold 4 bikes, the bike rack part can be switched out for a ski rack. The install/uninstall from the hitch take 30 seconds. very convenient
:AK47:Trunk mounted bike racks are kind of a PITA and will scratch your runner! :wow2:
Get a hitch mounted rack if cost is an issue get a roof mounted rack.
These are good hitch mounted options
kuat nv
thule t2
saris thelma
1upusa
This is my setup
kuat nv (got it used for $300
<a href="http://s1106.beta.photobucket.com/user/Ridefast84/media/IMG_1239_zps05858672.jpg.html" target="_blank"><img src="http://i1106.photobucket.com/albums/h377/Ridefast84/IMG_1239_zps05858672.jpg" border="0" alt=" photo IMG_1239_zps05858672.jpg"/></a>
If you want something cheap and reliable right away for $139 get the rocky mounts tie rod for the roof. Just don't forget your bike is on the roof and drive into the garage or a overhang at a drive thru.
I'm a huge fan of my Thule hitch rack. Tray racks are the best because they hold any size and shape of bike. A little pricey, but very high quality. Takes about 20 seconds to load or unload a bike. Even with the rack loaded up, you can hit a lever and drop it down to get the tailgate open.