I would first check on any zoning laws where you'll be parked and inquire about having a Park Model on the property. A Park Model would be built a little better than a cheapie trailer. You can get used Park Models if you drive through an RV park with Park Models.
I would definitely want double pane windows. Keeping your water connections/piping will be an issue so you'll have to protect them. Propane will be a big expense for heating. If you're in an area that gets heavy wet snowfall, you will have to keep your roof cleared as the extra weight wouldn't be good...same if you have slideouts...melting and freezing could allow water to seep in. You'll definitely want to put some insulated skirting around the bottom along with mice/pack rat protection. They'll love it! :) Best of luck to you.
