a dedicated ski boat requires deep water as they draw a bit for the rudder and prop. remember that when you are looking at older mastercrafts or ski nautiques. They also are extremely specific to skiing. they will pull up to a dozen skiers right up to 35mph..... no more. boats like the ProStar or MariStar would be good boats if you find a well cared for one as your budget has you looking at 25-30 year old examples of well-cared for ski boats.
I personally like 2-strokes over 4-strokes when it comes to outboards, however that is my preference.
as far as dedicated ski boats, you wont find one in aluminum. you will find bow riders though. Most can be skied behind, pull a tube, go fishing, go cruising, etc.
there are older dedicated outboard ski boats such as Switzercraft Hugger, Hustler, HydroStream, etc. these are found in one of 3 conditions. Needing a lot of work, Pristine, and claimed pristine, but needing a lot of work. They have balsa cored hulls, so consider most of them a project