I guess what I am looking for is the smallest possible boat that still has a berth I can sleep comfortably on with another person.
The other option is a boat you can modify. One of my previous yachts was only 25 feet, but by removing the toilet and a hanging locker I was able to have a reasonably big bed.
It was a popular 1 design boat in Australia and my yacht became know as the one with the "passion pit".
Unfortunately often the front bulkhead is structural so this cannot be done on all boats.
The saloon can also be easily modified, on most yachts, into a great bed area.
Not so good for entertaining, but this is mostly done outside anyway.