If all you want is to be able to take people out and ski and tube, you can get by with a 17 foot bowrider. A few adults and coolers will fill that up quick though, so if you don't plan to be at a place where you can pick people up and drop them off at shore, you'll want something bigger. If money is no object, chapparell makes some 23 ft bowriders that also have a head, fresh water washdown, sink, etc. that will hold 12 people comfortably with a cooler or two.
As far as being a money pit, if you are going to be using it in freshwater and get a quality boat with a reasonably new motor, it's really not that bad if you don't defer maintenance. Of course, with the question your asking, I'm guessing you don't have much boating experience, so there's a pretty decent chance you will 17 something up. I'd try to take somebody knowledgeable with you the first few times you take it out. There will inevitably be stuff you learn only by 17ing up, but the longer you have somebody teach you, the more likely it will be minor 17-ups and not things that will seriously damage your boat or injure somebody.