Further thinking, I am thinking it could be a scam to get your card info to steal your identity.

Never give him your credit card number.

i would imagine that no, sounds like he just doesn't want to face the fact that its his fault. call airbnb, whether you are using their site or not makes no difference, say you are interested in renting your house. ask if you are required to leave a double of the keys somewhere in case the renters lock themselves out. they are a big company so they will already have done their homework and know the law about this.

It would depend on your contract with him, but he was the one that locked himself out so let him be an adult and handle it.

I'm so sorry. I know this is really rough.

You shouldn’t pay because he can’t think about what he’s doing. I’d tell him no.

It is his responsibility, not yours. You provided a set of keys, no spares are needed.

I don't believe it's you who should pay ... Simple

Absolutely not. He's the one who's responsible for the key. If he wants to get back in, he should have to pay the locksmith for getting him in. Irresponsibility comes with a price.

No, you're not under a duty go supply spare keys. I could see you verifying him to a locksmith but the cost of loss is on him. He broke it.

that sounds all sorts of goofy.

dont pay

When you give your tenant keys, always give a spare set. In this one instance, you are responsible. In future, you will always give a spare set. That being said, the guy is an ass for not making his own spare set when he saw that you only gave him one set.

AND now you will have to change the locks when you get home.

How is it your resposibility?