Or do use it hunting?
Once again...for home shotgun pwnage---roll with a Benelli M1S90 or its much cheaper (but mechanically similar) counterpart the Beretta 1200/1201 with a pistol-gripped stock.
Super-fast and super deadly.
Remington 870 is arguably the most popular shotgun in the world, and very popular amongst police forces. It's certainly durable, readily available, inexpensive, and highly customizable.
If you look carefully, you should be able to find a brand new one at any number of stores for the mid to upper 200's. Most of them will come with the usual 28" barrel, but you can easily buy another 18" barrel for your shotgun. It takes all of 30 seconds to swap out barrels.
Since I have my own house, with sturdy walls, mine is loaded with 5 rounds of Federal "tactical" 00 buckshot. Even though it's a slower load than your standard 00 buckshot, it's very easy to fire, and I have full faith that 9 pellets hitting the target are going to do the job.
On another note, people who claim that you "rack the slide to scare off the intruder" are kidding only themselves, when it comes to the 870. From what I've seen, you can only load the magazine once you've already manually chambered the first shell. Depressing the lever to allow you to rack the slide would result in simply ejecting a live shell. Or did they change this in recent years?