A backup way to heat your house is a good idea. In addition, you may want to seal off parts of the house and heat smaller area. You can do this with tarps, roll plastic or extra blankets. I have a fireplace insert that is good for saving money in the wintertime as a supplement to the furnace. The fan runs on electricity, though, so I also have an old stand-alone wood stove. I bought the flue, elbows and damper to set it up with for less than $20. My House already has an extra chimney, since it was a very old house. Just having the materials and tools to build what you need is enough to start with. It doesn't have to be perfect right now. Just make sure that, when the time comes, you have the resources.

You may wish to run a generator for heat and electricity. If so you'll need appliances that don't use a lot of electricity. In addition to electric heaters to heat a couple of rooms, you may want to invest in a hot plate. You probably already have a crockpot, an electric skillet or similar low energy usage appliances. A regular kitchen stove draws a lot of electricity, so that won't be an option.