ROI on a Loft in an Airbnb

I am currently working on building a 480sqft 1 bedroom, 1 bathroom unit in the backyard of a rental property. Initially my goal was to have a loft with an extra bed in the unit to be more attractive for short term renters. What initially seemed to be a low cost addition is looking to become much more expensive as the roof pitch as is will not support it. For those using Airbnb or similar sites, do you find adding and extra bed even if it is not an extra room to increase your rate or decrease your vacancy?

Thanks in advance!