The advice is good... talk to people who liveaboard.... visit their boats and make a mental note of what you like and don't like. keep a list of likes and dislikes. Its like buying a house...You don't need to know exactly what you want (but you gotta have a very good idea).
One really good point made is to figure out early on your intended use: is is this going to be a "houseboat" that rarily leaves the dock or are you going to sail regularly. Generally the wider the boat, the more comfortable belowdeck but they tend not to be as fast (may or may not be an issue) and have a higher fuel consumption.
If space and natural light are important, you can also look at catamarans but that is also a compromise (and more expensive too).
Sail vs motor is also a personal choice. A sailing week-end out on a sailboat essentially costs you the food (and cooking gas). I won't speculate what a week-end out on a comparably sized "motored" yacht costs in fuel alone.
Good luck with your search!
Now based in Barbados.... and wait for it.....the boat is too!
Waymar - Jeanneau, Attalia