Hi,
We have two locks on our unit...
One lock is the "key" lock that all guests have access to...
The second is a keyed bolt lock (bolted from inside, keyed from outside) however, only the owner and us/cleaner have a copy...maybe you could offer this?
Keep in mind, the guest should expect to pay, between lock and locksmith, it is about a $350 investment.
As @Guy991 mentions, best not to create the opportunity for guest to lock you out. 😞