Many times I get requests for usage of my photos or even complete articles. Often, no payment is offered, as ‘the budget is low‘, ‘we are non-profit‘, ‘we will give a credit in return, which will be good for you!‘ and other, similar motivations.
Photography is a profession, we need to make a living and websites and cameras cannot be bought with ‘credits’. Photographers are often helping out people who need it, but any charity or non-profit that pays thousands of dollars in salary to each member of their management team (would they agree to work for ‘credit’?), can also afford to pay for photography.
Tony Wu has written a standard answer down that can be sent by photographers, which covers everything: