otherwise it seems too easy to get a house in skyrim.. or at least that is what it sounds like.
That's what I didn't really like about "home owning" in Morrowind. Slaughter inhabitants -> free, fully furnished home with welcoming gifts.
I'd hope that if you kill a house's inhabitants, entering that house at any time afterward would be considered tresspassing, and anything you leave in there would be removed after a couple days. This would be to discourage "free housing" and encourage buying a house properly. My thinking would be that if a house becomes uninhabited, then ownership defaults to the town/hold/province, and they wouldn't want people just waltzing in and using it for free. They'd also do regular audits and clear out junk that is left in there. You could sleep in the beds and stuff, sure, but you're still not legally allowed in the house.
Going off this, an interesting idea would be that if a home is made uninhabited (and you didn't get caught murdering them), then it becomes available to buy later on for an appropriate price. Diabolical players still have the ability to get the house they want through immoral means, and free housing is still discouraged.