Do recos from NGO managers count as professional letters of recommendation if you are not working there full time and not drawing a salary? Do professional recos need to come only from full time employers?
Not necessarily. But it depends on the school though.
For ex, Booth says that one letter has to be professional( the place where you are working). If you are working for a NGO full-time and not drawing a salary, a reco from your supervisor falls under this category.
The second reco can also be from your existing company or from the place where you've worked earlier or from a volunteer project you worked on or from a club that you are part of.
The intent is to showcase your personality from different angles. So, just take a call based on your app strategy