Jeff, if you are serious about buying this Hobie 20, be sure you get the owner to come out and sail with you at least once or twice before you try to go it alone. Everyone here has a horror story to tell about some newbie who showed up with a new (to him) cat when it was blowing 20, with the wife and kid, and shortly after was never seen sailing again...
When these things flip, (and as a newbie, you will, unless you get lots of good instruction or only go out on very light air days) they do not stay still. They project a huge barn door of a trampoline to the wind and will be moving downwind quickly, with or without you. Keep that in mind when you and the family hit the water. Have the wife swim for the kid while you hold onto the boat, sail back for them after you right it, but as many have said, you will have trouble righting it alone. It can be done if everything works, but you have to know what you are doing ahead of time.
Read the short article I just posted about the America's Cup crews, the best mono sailors in the world, trying to figure out mulithulls. Guess what, even they flipped it. So be sure the wind isn't blowing too hard (no more than 10 the first few times out) and be sure it's an -onshore- breaze, as that's where you will be headded when the boat leaves you in the water. We've all done it. <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />