a couple of observations:
1. I assume you want to buy a motorboat and not a sailboat. To me motorboats are boring. Sailing on the other hand is challenging and fascinating because no matter how much you have sailed, or how much you have learned about sailing, there is always more to learn, lots more.
2. Having your wife be the chief instigator and promoter for getting a boat is a huge advantage. Most of the time we guys have to sell our skeptical wives on getting a boat. My best selling point proved to be that sailing is something we can all, the whole family, do together. And it has proven to be true. I think this is one of the reasons my wife has accepted sailing, despite her initial doubts.
When I first started looking for boats, I looked at a lot of used ones. Most of the time when I asked the owner why he was selling the boat, he gave some reason connected to his wife's objections to having a boat.
I ended up buying a new one. If you do decide on a used boat, and there can be some real bargains, be sure to have a specialist survey your boat for you before you buy. Among other things, he will point out all the potential problems you might not have noticed.
One interesting sidelight: women can - and often do - become jealous of boats. This is definitely true for sailboats. It may also be true for motorboats. Women come to resent the amount of time, money, and attention that you devote to the boat. After all, it is time, money, and attention that you are not devoting to her.
One more observation on this: women almost always look better on a boat.
3. If you buy a used boat you can save a lot up front, but the maintenance costs will also be greater. New or used, be sure to include maintenance costs, beyond storage and fuel, in trying to calculate your annual budget. Stuff breaks on boats, that's just the way it is.
4. If finances are a major consideration in buying a boat, don't buy. Boating is about enjoyment, not money.