How many entrances are there? Is there more than one door? The wards are to keep others out not in. If there were a fire or something you can get out like normal. You don't need the key to get out. You can still open windows or sliding glass doors and regular doors and get out. If someone stole it, yes, they could get in. If that happened let me know and I'll put up new wards and have a new key. Yes, visitors can come in like normal when you invite them over. You won't see the wards. You need a revelation charm and charmed lense or again, a powerful magic person.