I used to put my MTB in the back of my Fit before I got a roof rack. I did many of the things mentioned here as well, bought cheapo black bath towels at WalMart to wrap the bike in and protect the sides of the car. Scratched up one of the panels when some part was rubbing on the side of the car in the trunk. Another thing to watch out for is your back bumper. I forget if Rav4's have a bumper protector on the top (it was optional on my Fit) and if you're having trouble hiking it up into the car it's really easy to scratch the paint off if the pedal catches the lip of the bumper. After riding I know I was too tired to lift the pedal up and over a few times and have some nice paint chips on my bumper, unfortunately it was black under the silver paint so it looks really bad and the dealer is always out of touch up paint to buy.

Consider keeping an eye on craigslist for used bike racks. REI has car racks on sale right now (it's only once or twice a year) so as people upgrade you might find their old racks for sale. Most of my racks came secondhand as my mom's boyfriend upgraded all of his gear the last few years.