RWD is great for towing and recommended especially for boats. It used to be that framed vehicles were better, but that’s blurred now. The cheapest I can think of that would work on a slippery boat ramp is a 2wd/rwd compact truck with a limited slip rear differential which I used for years carting boats of the weight you stated. It will give you all the traction you need and the added safety you can’t get with fwd. An AWD Subaru/RAV4/CRV for occasional towing would be acceptable. 4 wd drive is better traction wise, but unless you really need it otherwise, is an unnecessary expense. Limited slip is actually better than part time 4 wd in some traction situations, especially climbing hills. Locking two rear wheels when the center of gravity shifts to the rear going up hill is sometimes better then engaging one wheel on front and one on back which is the case with part time and most AWD w/o traction control. I know this with experience driving trucks and vans and Tractor/truck makers knew this for years.
A used performance rwd car with limited slip is another option; with the right tires of course. A RWD Mustang has potential with that add on.