Like Tomcat above, I have a GTX three-seater and an RXP two-seater. The GTX is an '97 and the RXP is an '05. I was able to buy them both used for $10,000.
I might suggest to you that you get one three-seater and then one two-seater. That way you get the best of both worlds.
In Sea-Doo sense, the GTX would be the 4-door Cadillac. An XP or RXP would be the Ferrari.
XPs are best for one person only. An RXP handles two people very well.
If you are going to get two Sea-Doos, then I would suggest getting two that have the same engine... If you are handy mechanically and like to work on stuff, then you would like the two-stroke engine models. Probably the 951 engine that has 130hp. In general, you would be looking for something manufactured between 1999 and 2003 (with some exceptions). The 3-seater models in this age range are the GTX and GTI. A really fun 2-seater is the GSX (great hull - really fast). The RX is another 2-seater. The one person sport model is the XP.
If you are patient, you can find a good deal on a ski with the 4-stroke engine like an 04-08 RXP, RXT, GTI, GTX, & Wake. I got my '05 RXP (215 supercharged) with trailer for $7000. If you get one of these Supercharged 4-stroke models, keep in mind that you will probably have to spend another $500-$700 having the ceramic clutch washers in the supercharger changed to steel washers. There have been several instances where the ceramic washers broke and trashed the engine.
If you are going to be pulling tubes a lot, you should probably seriously consider looking for the Wake model ski. It has an extendable pylon that raises up to connect your tow rope to. This is very important as tow ropes have a tendency to get caught in the wake when the rope is connected low on the ski. My sons and I found this out the hard way.
Good luck!