Legal advice on renting a house?

You have to rent the house to someone else. Someone called to look at the house in the name of looking at the house. After he took your house key, the phone couldn't get through again. The countermeasures in this case are as follows:

First, if he doesn't want to rent a house for other reasons after taking the key, he doesn't use your house without authorization. And I won't give you your keys back. In this case, if you have received the certificate of your key, you can sue the people's court and ask him to return it to you. However, it will take a long time to prosecute such a trivial matter. If you want to rent it to others, you'd better change a key yourself.

If he took your key, he checked in without signing a lease contract with you or your consent. This is illegal. You can call the police immediately.