"He is also a salesman."
Translation:C'est aussi un vendeur.
I for one don't see "aussi" as a modifier of a noun. Last I heard "aussi" meant "also," which is an adverb. The rest of the rules mentioned on that page don't apply whatsoever.
You may forget about the adverb, the important thing is that there is a noun after verb être.
- he is selling apples, he is nice, he is a salesman: il vend des pommes, il est gentil, c'est un vendeur.