A DIYer once dreamt of constructing a treehouse on his land before his own house was even built. Now, with multiple accommodations on the property, the treehouse has become a reality, and a legitimate source of income. Getting Off The Ground: Will Sutherland built a treehouse in his backyard in six months’ time. It’s super popular on Airbnb Inc (NASDAQ: ABNB), bringing in an average of $30,000 per year on the platform, according to a Business Insider report. He saved money on the build by doing all the work himself and sourcing a lot of the material from a friend who was in the process of buil…