‘Friend’ is using a guy he met

So I’ve got this friend who’s been using a guy he met online for money, it’s this guys first gay relationship and he’s head over heels for him. This friend has constantly been using him for money, clothes, new phone and nights out. Just this week he has had over £600 off him and He has also slept with two people since they got together.. they’ve only been together a month. But whatever this friend says the guy does because he thinks he’s in love but the friend only wants him for money, I feel so bad knowing what this friend is doing but he just doesn’t listen when he gets told. What can I do?