Look for a source of coal that you can easily extract near buy. There are many small coal deposits that are too small to be commercially viable.
But these small deposits on the surface that can be mined easily will keep you warm and cozy for years.
Get a generator and some batteries you can charge. If you want a renewable, get a small battery charging windmill that you can buy for 400-800 dollars with self-installation.
I don’t know if there is any coal around where I live. This is or was once a huge copper mining area. We don’t have mineral rights on our property below a certain level. Not sure how many feet down.
I would not recommend digging coal on your own land. The permit process will require months of work by a geologist and a PE to meet Department of Interior requirements.