Like FW I dont have facebook but can look at the general set up which look amazing. Certainly what you suggest is a proposition I would have been interested in but realistically it would have been for a week maximum rather than a few weeks as you seem to really want.
I would be sure that advertising it as a 'working week for free accommodation' ,and perhaps some direction on what to do in the area for the rest of the time , would be very a very attractive option. I spent so many of my holidays as a child and young adult in and around Bala. It is a breathtakingly beautiful part of the world.
Good luck.
......where is the beer shop?
Greg