I have a similar problem in one of my cottages...there is a sleeper sofa, (not made up) & a queen bed in the bedroom...people go rummaging through my sheets, find one & make up the sleeper sofa (which is not the most comfortable thing--as those of you who are familiar with sofa beds, can attest).... So my laundry has doubled with no additional income...
For your situation, I suggest getting a generic bedspread & making up the extra bed as a "prop" or "dummy" bed...Although don't count out the possibility that people may sleep on it using only the bedspread as a cover....ick....I especially hate it when guests sleep on my sofas with no sheets, using only a quilt or blanket as cover