Full Time Cold Weather
While Beth has made some really good points, I would like to comment more directly on your situation.
If you do get the Discovery, or another recent class A motorhome you will have your waste tanks and your plumbing in enclosed, heated bays where as long as you keep the interior of the motorhome reasonably comfortable for you,it will also keep the bays above freezing. That is because those bays have a small heat duct from the furnace that dumps into them. But you will use a lot of propane and you won't want to drive the motorhome to the supply of propane. For that you need to have a connection for an external tank. There is a kit available from most RV supply stores called "Extend a Stay" that will allow you to connect an external tank to your rig above the regulator so that you will not need another regulator. You will want at least one tank of 100# or more, and you might even check on a "keep full" service from the propane suppliers. Most of them do rent tanks. Since you will be paying your own electricty, you will probably not want to use electric heat to any large degree as it will most likely cost more than the propane. There are catylitic heaters that use propane that are much more efficient at heating than the installed forced air furnaces that come in an RV.
If you are still in the buying process, be sure to get the dual pane windows as that will not only help a lot in the cost of heat, but it also helps a lot with another problem of cold weather RV living, condensation. With the dual pane windows we only have to deal with condensation on the aluminum frames and the windshield. But to help to cut down on that problem, be sure to open a vent in the bathroom when showering and use the vent hood when cooking. An RV is a very small space and with just your breath and cooking it will soon have very high humidity.
If you are planning to buy a lot for the RV, put the utilities into a curb like island in the center of the pad so that you can crawl under the rig and connect, and thus when you add some type of skirting around the RV to prevent wind under the rig, it will also protect the water and sewer connections. The Discovery will have all of the valves for water and sewer inside of one heated bay so with the RV skirt installed, those will be protected. And do plan to install some type of scirting. If you are on an owned lot, make it from some weather proof material and line it with the foil wrapped foam that is used in the construction industry. You can then build some type of storage for the skirt when not in use. While straw is a good insulating material, it is also a fire hazard and it is difficult to adjust the highth of it to fit the motorhome. And you will need to block the wheel wells as well.
On the subject of wheels, keep your tires isolated from the moisture of the earth with plastic or some kind of water proof material. Tires will weather best if they are not allowed to stay damp for long periods. And they should also be protected from the sun, but skirting can do that. I keep tire covers on all of my wheels when we are parked for more than a few days.
You will probably want to have some way to insulate the windshield extra since it is the one window that you can't get with dual pane glass. We use heavy quilted drapes made by my wife with the quilting filled with Thinsulite(3M Co.) like is used in winter coats. Another way is to use the foil coated bubble material. But you will need to open it up and use an ocillating fan to dry out any moisture once a week or so.
These ideas should help you as you plan for your winter living. Hopefully there will be other posts that will cover the things that we have not yet thought of.