@Laura-Plourde0,
Since we had to ship all of the furnishings for our rentals from the US, space and packaging were big considerations, in addition to cost. We purchased 12-13" king hybrid mattresses-in-a-box, and usually get great compliments about the comfort. The average cost was about $400, and were purchased on different sites, Amazon, Sam's Club, Walmart, and Costco. They cannot be flipped over, but we do regularly rotate them 180 degrees to change the head and foot of the beds. Mattress comfort is subjective, and we've had guests tell us that a mattress is too soft/firm, but the preceding and next guest say that they didn't want to get out of the bed during their stay. We have three layers of mattress protection: zippered mattress encasement, waterproof mattress pad, and a mattress encasement with an elastic band. The mattresses are almost 4 years old and are in such good condition that when we had our health inspection in March the inspector thought the mattresses were new. We also put zippered pillowcase encasements over the pillows.