I am surprised to find the word prends and not prend in this French construction, especially considering the English parallel.
Qui prend l'argent? C'est moi qui prends l'argent.
Who is taking the money? It is I who takes the money.
If you look closely, you will notice that the French sentence uses a first-person verb (prends) whereas the English uses a third-person verb (takes). Is there some difference in the rules for relative clauses that would explain this?