I never cared for the saying, "beggars can't be choosers." It always seemed to imply that standards are a luxury. Whether it be food or art or people, if something is not good enough for you, then you can and should choose to not take it.
I was wrong, though, about the saying. It is a correct statement, but I look at it from the opposite direction. A beggar is one without standards (or with standards so low as to be negligible). That is why they beg. Beggars can't be choosers because they are mutually exclusive terms. A chooser is one who, by definition, is not begging.
What matters, though, is to realize when you are and when you are not a beggar.
Young writers are beggars of a sort. They will do anything to have anybody acknowledge them and validate their writing (and thus validate themselves). They sell their services for cheap (or give them away) to anybody willing to accept them. It is classic begging.
Be better than that. Be strong. Just because you do not have a writing job does not mean you have to take anything that remotely resembles it. If you are a skilled professional (and if you are able to do that work, then you are), act like one. Don't take a lousy deal just because it was the first or only one offered. Be a chooser.