We stored our 40' boat in heated storage in Michigan for several years. I simply drained the fresh water tank and made sure the black tank was drained and clean. Of course we also threw tons of softner sheets all over to keep mice out and things smelling good.
Most heated storage places will bring in a generator if utilities fail, otherwise they would tell you to winterize.
Full Time in 2017 Newmar Ventana 4369
pulling a 24' enclosed (Mini Cooper/Harley/Kayak)
(traded 2014 Thor Challenger)
US Army 70-73 Retired LEO