All good advice so far. I've demoed literally over a hundred houses since one of my occupations is demolition contractor. FIRST, get everything straight with the insurance or you could end up doing a lot of work for nothing.
I've had several burned by fire departments, and it's a 50/50 whether you end up with a bigger mess at the end.
Contractors will usually give you an estimate
. The smaller the house, the higher the cost per square foot and burned out houses are a little higher than others because of the mess to deal with. I'd be looking for a price of around $3.50 to $4 per square foot. This is because it costs to move and set up equipment just the same on a small building as a large one.
This size is really easily doable yourself with mostly hand tools, chain hoists, sledge hammer, crowbar, chainsaw especially since it's crawlspace. You can probably pull it over with a truck and chains to get your work on the ground. Your costs are going to be landfill and most likely rental of a loader/bobcat. Landfill prices are all over the place. You might see something like $35 per ton for regular lined landfill, but check around until you find a C&D (construction and demolition) landfill or section of another designated as such. You might get the price down to $12 per ton or even a sweet deal like $100 per truck load (get a big truck). This house should fit in one dump semi trailer or large roll off if you go that way.
Warning: You must file a notice of demolition with your state EPA. (Alabama's is ADEM) They will let you permit to tear it down, but not if you do it before calling them.
Next, you might want to make sure you don't have asbestos. That stuff can cause you real grief and is dangerous. If you do it wrong, you might have to have an asbestos abatement company remove it and that can cost the same as tearing the whole house down. Check for that hard fiber siding and 6 inch lenolium type floor tile. You may remove it yourself as a homeowner, but you need to find out your local rules for disposal. This stuff has cost me the entire profit and more on a few jobs where we found extra asbestos that wasn't included in the survey.
You can do it yourself, just be careful and follow the local rules.