@Elaine701 My response was mostly a reply to the first response, that suggested that the host has to explain why they will or won't allow early check-in. I thought that was very bad guidance for a new host. It creates a mindset of mollifying or appeasing demanding guests, when a more business-like approach can be beneficial.
In short, it's up to a host or hotel whether they do or don't allow early check-in, but there is no obligation to explain to a guest the reasoning behind that decision.
I also thought that advising the OP to have early check-in fees disclosed in the listing was poor advice, because it then advertises that early check-in is a "thing."
I don't think there's any obligation to do that, because, as I mentioned, it's outside of the terms of the booking agreement, and the host can choose to charge (or not) as he or she sees fit.