To pull a waterskier, you'll need minimum of 40hp. That includes driver and spotter on board too, so I'd say 4.0 - 4.5m is the size you should consider. Plenty examples on the market including Zodiac Pro, Humber Assault (both shallow V hulls) which are fine for calm days but do tend to slap in the rough stuff. Avon Searider 4.0 sets the benchmark for a deep V RIB at this size. Again there are plenty decent, and of course used and abused examples out there.
Be wary of buying from Ebay or Gumtree unless you've done your research first. See the boat in daylight and the see the engine running from cold. Get receipts and plenty of them to check history and maintenance schedules.
Wills Marine have a couple of boats that would fit the bill at the cheaper end of the scale. You could of course consider a SIB with 40hp that's trailered with aluminium HD floor. Just a thought.
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