سلام علیکم

I have a major question. I know someone personally who is running an NGO. The NGO is doing pretty well. However, the family is running their home with the donation money too.

Does Islam allow us to do that? If yes, how much % of the money can the NGO use for their personal/family development. Or is it not allowed? If not then how on earth can that person feed the family because the person is giving his all time to the NGO for welfare work.

Thanks
Ibad