What should I look for when renting a houseboat for a vacation?

I'm thinking about renting a houseboat for a vacation this summer or next. It would be for my and two kids (14 & 10) and we thought we'd take another couple to split the costs and their two kids (16 & 10). What do I want to be looking for when I rent a houseboat? Any special amenities? Do most rental companies let you tow a fishing boat or jet-skis with the boat? Any help would be appreciated. Thanks!