Re: looking to buy a used boat
there is a world of difference between a 17' and a 25'. The differences in price range, handling, storage and maintenance, trailer and tow vehicle requirements, and difficulty if you trailer it. The question still can't be answered.
Let me suggest you go to a website of a boat manufacturer that makes boats from 17' to 25'. Look at the difference in price, size, motor, weight. You will get a better idea of what you want, realistically, and what you can handle based on skill, money, towing ans storage limitations. Price out insurance, registration and storage. Look at fuel consumption--6 gallons an hour makes an expensive day's trip.
Try Boston Whaler, Grady White, Carolina Skiff/Sea Chaser, Sea Hunt, Palm beach, Tahoe, Bayliner, Sea Ray--I think they each cover your range.
Note that you can buy a fairly new used boat for 75% of the new price and a decent used model for 50% of new. But the best place to start is the new ones to learn design options, etc. Be sure you are sitting down when you look at the prices.
Although lots of people do it, I think 25' is too big to trailer and launch every time you use it, and too big for a learner. I'd start at 17-19'. You can also usually stay on a single axle that way.