The very first thing that you need to think about is your safety and the safety of the others in the house that you live in. That also includes any small children that may get a hold of such a thing.Then why non-lethal? Because you would rather not kill a person, if that is your view I completely respect that, or is it the permit issue? Tazers and other non lethal devices can kill or seriously injure a child as easy as a gun. You will need to think about where to store it, how easy it will be for you to get to it, and how effective it will be. They make guns that shoot rubber bullets, or nets that are very effective, but they cost a lot. The cheapest and most reliable device you could use is a 12 gage shotgun. Typically there is no permit issues because they are primarily used for hunting. You can get them with shorter stocks and barrels so they are easier to maneuver in your home. Remember what ever is dangerous to intruders is dangerous to you. If this device is not strong enough to keep them under control until help comes then you only have an angry, injured, criminal which is not a good thing to have in your house.