.edu is right, all depends on keywords. If it's something like a Brazilian Snake Rescue site, then you're better off doing what smh7233 said...
As far as parking, you're not likely going to get much more than $2 a click for anything you park... if you park a loan site at Sedo or a similar strong keyword, you'll likely have about 3 advertisers who will make YOU (sedo gets more, but sedo will pay you) - $1.50-$2 or so a click... and the other 7 will make you like $0.35-$1.00 a click..
It's my experience that that's usually the case with parking - some of the advertisers pay much more than others but all those links will be on your page. I could be wrong, but that;s what it seems like. If you have a ton of traffic, you're probably better off with adsense.