If your not hurting for the money it's up to you, I don't think I would, but it's not the end of the world to some sellers. If your even considering it, then it may not bother you so much, worst case he doesn't pay and you block anyway?
In the end it's just a call you'll have to make, I know some books are slow sellers, and "if" it may not sell in that weeks time at least you have his "word"... still that is kind of a what if game.
I don't think it would be a "scam" to wait a week, the having someone else pay and in person is a red flag, but still if your not minding waiting a week. As is, he hasn't paid, and no harm in cancelling the sale and blocking. No waiting for a refund and etc hassle.
Might as well cancel and block but sometimes we "like to give the benefit of the doubt" but ya it's red flag