To reply to 2) and 3)
2) Anything from 24' and up is weekendable. But if you live in Vancouver, it's a long way to the Oregon
coast! And the outside coast of BC, Wash, and Oregon is a lot more rugged than the Gulf and San Juan islands
. Stick with them until you get a lot more experience.
Your biggest trouble right now in Vancouver is getting affordable (or any) moorage, so see if you can buy a boat with an assumable moorage.
Best bets on typical weekender type boats (assuming you don't keep the first boat forever) is a well recognized brand name so that you have good resale value and lots of other owners for support. Maybe a Catalina
or a Beneteau
(both have average quality but good boat for buck ratio)
3) Boat building is a lot different than RVs. RV construction makes me shudder (no disrespect intended but they are not generally well put together). People have built all kinds of boats but it takes many years to build an average 30' boat for example. It makes more sense (time and money) to buy a used boat
and fix it up. Boat building only makes sense if you WANT desperately to build a boat for its own sake.
A minimal length boat is probably around 30'. My wife and I cruised one for 4 years in Mexico/Central America /Carib. and lived aboard for another 4 years. We know of 2 other couples on a Westsail 28 and Vancouver 27, both heavy boats with lots of room, but poor sailing boats that will be overloaded with a typical couple's payload.