According to my friend, flat salary contracts are required to meet minimum wage standards when divided by the number of hours of labor.
Additionally, room and board or other amenities are not valued highly by labor courts in most cases (specifically, you can only count their actual value, not what you charge campers – and actual value is difficult to prove). Finally, even signing a contract does not waive your rights as far as wages.
I don’t claim any expertise personally, I am just quoting an expert in the field.