Are you planning to leave water in the storage tanks?
If the answer is no...then basically you are just storing it outside, which plenty of people do. drain the lines best you can and run some anti-freeze and you should be fine.
if the answer is yes...well it would take a heck of a lot of anti-freeze to keep whatever is int he black and grey tanks from freezing.
2013 Coachmen Freedom Express 320BHDS pulled by a 2005 F250 King Ranch CC
A rainy day camping is better than a sunny day at work.