I use only padlocks to lock the grille door and gate. So my contractor only need keys to main gate padlock, main grille padlock and the wooden main door. To save money, I bought those cheap padlock from Tesco, the type that one key can open 3 padlocks. After finish renovation only change to better padlocks.

Only recently I found out my contractor also didn't come to my house, open the door for his sub contractors and close after this. He actually put the keys inside the mailbox and let them take by themselves! So better don't put anything, anything at all in your new house. I was angry with my contractor for not monitoring their work, so I took back the keys and ask them to come on Saturday only, or when I can take leave to monitor them.