Requirements for people hauled?
GM Fullsize SUV is a great choice IMO. They're tough as nails, easy to work on, and tow really well. Not gonna get the latest tech, or all the lane assist and that kind of stuff, but they'll get you to the lake and back for not much money.
This one needs a little TLC, but would pull your boat around just fine and still has some life left in it. Many more examples out there of this vintage/condition in this $5k range. Make sure you get one with the 3.73 rear gears (check the RPO codes in the glove box to verify), the ones with the 3.42's are only rated at like 4,600lbs or something. Mine was rated at 7,800lbs I think.
I had a 2003 Yukon. Bought it with 18k miles, traded away for a Focus (what a bad move that was) in 2012 with 186k miles. I think I put spark plugs, intake gasket, A/C compressor, Fan resistor bank, and a wheel bearing on it. The rest was just regular maintenance items (oil change, trans fluid, rear diff fluid, brakes/pads, etc) over the 4 years or so I had it. Towed car trailers as far south as El Paso, and as far north as Milwaukee. Made several vacation trips to the beach in South Carolina. Was a great vehicle for us, traded it because my commute went from 10 mi/day to 112mi/day and that was right when gas was nearing $4/gal. Once towed a 28ft enclosed trailer to South Bend in January. Ambient temps never got above 0deg F and the trans never broke 100deg F for the full loaded trip. Was a really good SUV.
With that said, I'm in a full size pickup now, and will never go back to an SUV. $800 locking and waterproof cover gives me all the dry storage I need, has the same number of seats as my Yukon, gets a little better mileage, and the visibility is much better. That same early '00's vintage GM pickup can be found for much less cash, but watch out for rust and high (over 250k) miles.
How mechanically inclined are you and how much time do you have? A good friend of mind has a '95 Tahoe that we have literally been trying to destroy for the last few years. We've done some pretty harsh things to it, and it's still running just fine. He drove it without coolant for 3 days this winter because it was too cold to fix the hose and deal with it outside and he wanted to see if it would survive. It's got like 450k miles on it now and is still running. If you have some time to put some effort into a machine, these can be found for $1k or less.