@Leah502 welcome!
Although many will say you should charge for early check-in I never do. If I can offer it, I will, but i only confirm it the day before arrival. So i let the guest know that the cottage is booked before them and I have to do the turnover to prep for their arrival. (this is really just to remind them that my place isn't sitting empty, and I only have the one cottage to offer them, cos we aren't a hotel).
I call it "complimentary early arrival"
1) this lets them know they are getting some extra, for free, yay.
2) i use 'arrival' instead of 'check-in' because i try to get away from hotel language. It's just a subtle way to train guests into the notion that STR are different.
how much would you reasonably charge a guest for early check-in? $25-50? is this worth it? oh and remember there'll be a guest surcharge on that fee. I'd rather give the guest this bit of extra value and hope it gives me a good review.
Another option: (never had any takers though), I've offered them a 50% discount on the night before their reservation date (if available).
The majority of guests who ask for early check-in never make it here early anyway. It's usually further to drive than they think, and they take it slow enjoying the countryside, and stop for lunch. Happens so much i will often grant early arrival to guests who are arriving by plane, hiring a car and claiming they'll be up to us by midday (it's a 1 hour drive). LOL. So I say 'sure' and so far 100% of the time they arrive late in the afternoon.
