Re: How long did you wait before buying?
Although I am a life-long boater, when I decided to move up to a larger/nicer boat, it went about like this:
Start with a month of looking at boats I wasn't going to actually buy, at dealers, marinas, manufacturer's web sites, etc., with family input, to decide what size/style we wanted. There is no substitute for climbing around on lots of them. Think dealerships and boat shows.
Then a couple of weeks of looking at all the ads in the region to get an idea on the market prices, the inventory, typical features and to see what would be the newest used boat that would fit in my budget. And also how fast they sold.
When I found one I liked, it was a couple of days to go look at it; a couple of days for a conditional offer (he needed to fix a trim tab and check the compression for me) and a couple of days to get my check to his credit union to clear the title. So really, less than a week--but because I had already done my homework, I could have bought the right boat in a couple of hours.
That's how you get the deals--be educated enough that you can jump on the deal immediately and without conditions. Know the cost of your risks (example; worst case, if I have to repower, I can still afford it and it's a good deal. Or factor in a replacement trailer if your great find is on a bad trailer) In my case, I didn't even need a sea trial.
Don't look at a boat and then figure out if you should buy it. Instead, look at all boats, narrow down to the one you want (including age and price range) and then go find it.
Note: I started in January when the market is slow, bought in March/April when it was heating up. You can't start the process on Memorial Day. Plus I live where there is a good market with lots of choices.
PS a year later I helped by sister/BIL buy one and go through the same process, and it worked well.