Randy is correct. When documenting reasons for denial, I've always offered this advice: Think about the true reason you are denying the application.
On the surface, you might say you're denying it because of the age of the applicant, but that's not really the reason. As Randy points out, you're denying it because you would not have a legally enforceable contract. It's OK to turn someone down for that reason, and it's not always related to age, so there's no disparate impact theory to worry about either.