I am not posting this as a slap to any one who wants to harden their home. I post this as a reasonable alternative for those who cannot afford it. If you can afford and do actually intend to truly "harden" your home OR you just like to fantasize or brainstorm about it, by all means don't let me stop you from posting about it here.
But the fact is...Unless you intend to go with 360 degree sandbags or 2 foot thick cement walls followed up with steel doors (and don't forget the roof), your home will never be hardened. And even if you do all of that, it is still likely you could be burned out!
May I suggest an option that is actually feasible to the average person reading this...
With minimum money and effort, 2 or more layers of chain link fencing, properly attached around windows and doors (from the inside) will do a lot to keep out or at least slow down the hordes. Of course it can be defeated with wire cutters, but they will have to cut it while standing in a hail of lead. Even the "hook one end of a chain to the fence and the other to the truck bumper" won't necessarily do a complete job of removing the fence for the would be intruders. The chain will only rip the place(s) of the fencing to which it is attached, leaving jagged metal for them to try to crawl through, while being shot at.
Chain link fencing by no means makes a "hardened bunker," but for minimum effort and money, it can do much to delay entry to a home.
NOTE: Be careful not to trap yourself inside, in case of fire.