Some lessons learned from me on storing furniture and "stuff" in a cold, snowy climate like MN, based on my personal experiences with stuff getting wet, mildewed, and ruined. Admittedly, everything was in storage for four years, but your stuff may end up in storage longer than you think right now. So here goes:
Put a very heavy sheet of vinyl on the floor of the storage unit, but all wooden furniture should also be propped up a bit on 2x4s or 2x6s, etc. so nothing touches the floor or even the floor vinyl covering. I had an expensive ding room table get wet on one side to the point it was not repairable, even though I put it on vinyl. If I had to do it again, i would also put it on something like a board or chunk of thick plastic and even put more vinyl on top of that.
All of my mattresses that were in vinyl mattress sleeves were also ruined by mildew. I don't know what I would do next time--maybe double bag them and put them up on something?? Best solution might be to just toss and buy new when I got a house???
Use high-quality plastic storage boxes, not the cheap ones, and make sure they are sealed on top. Add duck tape, if necessary. No air or moisture should be able to get in.
Find a friend or relative to store all "priceless" things like family photos and documents. That person should put them in a dry area like a closet, not a damp basement or storage place.
I would also suggest that you get all old photos, home movies, slides, etc transferred to electronic format. Give copies to relatives so you have backups. I have put the originals in a small safe at my son's house, and keep copies with me.
By the way, I initially committed to two years full-timing but have been on the road almost 7 years, with no plans to quit. And two years ago, I emptied that storage room, gave away or tossed almost everything and am down to 12 boxes of family things at my son's house. It was costing me more to store stuff than to replace it when I finally quit RVing.