Swissrose, do some comparisons of prices in your local area gunstores and take in a gunshow or two. It's worth the drive.
A used gun is 90+% of the time just as usable as a new one. And the price might well save 20% to 40% of new.
For home defense, a 20-gauge is as good as anything. Somebody might survive a load of #9 skeet inside of 30 feet, but they will no longer be actively hostile.
Not knowing what state you're in, I don't know your local laws about shooting. However, most states have no interest in what you do on your own property, outside of city limits. Merely call your local sheriff's office and tell them you'd like to do some practice shooting "out in the county" on your own land; any problems? I'd venture that if there is bird-hunting or deer-hunting in your state, you'd be okay.
Keep on askin' stuff