I have one of these Adams40s NowandZen so my opinion my be a bit one sided. They are a proven blue water boat with many having circumnavigated the world. I paid a lot more money for mine than this one is advertised and still had to do a lot of work. But even thought the prices have dropped a fair bit since I brought my boat,

beware. You need to be able to inspect every inch of the steel interior. Mine was rusting from the inside out, but the guy who surveyed it told me it was in very good condition. This boat may in fact be a good one but make sure you factor in all those other thing$ you consider essential when doing up your budget.
Being steel means they will be a bit slower than the fibreglass Adams of similar length but it also means you get a more comfortable ride in rough weather. They have a lower centre of gravity than some of the more roomy (higher freeboard) production boats, which also adds to a more comfortable ride because the cockpit is lower. There is over 6ft head room in the main cabin but not in the forward V-Berth or aft cabin.
And in line with what southace said, no matter how big the boat is, you will fill it up with gear and still wish for more stowage space.
Even with 2 able bodied sailors on board, the boat has to be set up so it can be sailed by one person. Your wife. My hands a full lifting the main sail around and I'm glad its not a 45 footer. The Adams40 were considered a fast cruising boat and the hull shape means they don't need a massive rig to do this. Most marinas you go into have lots of 12m berths and so there is usually always room when needed.
My opinion (for what it's worth) based on talking to other sailors is that for 2 sailors a 37 to 42 foot boat is about right.
The boat you have shown here is a shoal draft and may have a swing keel (centreboard). Make sure you have a good look at this. Moving parts under the waterline could be an issue if not maintained properly.
Later this year I'm planning/hoping to take my Adams40 to the West Coast of NZ South Island (weather permitting) to check out places like Milford Sound after spending some time around New Caledonia till summer comes on. I'm 100% confident in the boat, it's just the guy hanging onto the the wheel that concerns me.
Good luck with the hunt and keep the dream alive