The fee should be mostly irrelevant (but see also notes below) to your decision whether a letter is required or not. There are places that do not require a fee, for example. Also, I take a fee, but sometimes refund it if I see disqualifying factors (resulting in a denial) before running the credit check.
I am actually not sure of the legal requirement, and it may depend on your state, too. In WI, for example, you are not required to give the reason for denial. As a default, I always send a letter and then state a reason (or the main reasons, as sometimes you have a whole book of reasons ;)
I also reserve the right to deny an app simply because it is not complete. And not paying the fee means not complete. So if you have that, then the fee could become relevant as a reason, if you wish to use that.
The tenant asking for policies could be a red flag. It is always advisable to have a written policy and actually give that with the application forms. That way they cannot complain if they are being denied because of an eviction last year, since it was stated clearly. You are not required to have a written policy, but it's like an insurance. For example I heard of a landlord in the area who only rented to people with a certain min. income that was quite high. One day he denied a couple with kids, based on the income only. They sued for discrimination because of the kids, and they won. It came out that in the past, his tenants always happened to be couples with no kids (coincidence) and he could not provide a written policy that established a history for his reasons.
I am not saying you have that problem, but you have to check your state laws to see what's required. Otherwise, I would just send him (or both) a denial with the reasons (eviction), and don't bother about he policy. Did you state in the listing or somewhere else "no evictions?" You could refer to that.
Or you write up a brief half page list of bullet points with potential reasons for not approving and call it policy and send it (and use it in the future, too).