You may want to post a over capacity fee. For example...
You have reserved for 3 people.
The maximum capacity of your cabin is 4 people.
The extra charge (prepaid) for an extra person is $10 per night.
The extra charge (postpaid) for an extra person is $20 per night.
The extra charge (postpaid) for anyone over the 4 people is $200 per night.
Or version 2...
You have reserved for 3 people.
The maximum capacity of your cabin is 4 people.
The extra charge (prepaid) for an extra person is $10 per night.
Any person not listed on the reservation found on the property will be reported to the police for trespass. You will be escorted off the property, with no refund..
The problem with an over-capacity fee is that it implicitly says too many people is OK (i.e., you don't have a hard limit), it'll just cost a bit more.
If you really do have a hard limit, you have to enforce it -- if not in the immediate moment, then at least in the future by not letting them return.
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See, in my mind, I would rather not argue, just set a fee that makes it financially impractical. At $100 PER NIGHT, I just don't think there are that many people who will take you up on the offer. But if they do, increase the fee to $200. At least over time you will bank the money for the septic system.
Or, set a hard limit, warning them that they will be refused and will still have to pay.
I hate arguing with people. I hit them in the wallet.
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