One of the biggest obstacles millennial homebuyers face is getting enough money for a down payment. One company is willing to help them cover that cost, but with a catch. Seattle based start-up Loftium is waiving the down payment if homeowners agree to list one of their bedrooms on Airbnb, for at least one year. Yifan Zhang, co-founder of the company, says she hopes Loftium encourages more millennials to become homeowners. Loftium has raised $2.5 million in venture capital.