It completely depends upon the photographer. Your best bet, if you don’t want to spend a lot of money is ask around to your friends and relatives to see if anyone is a shutterbug that would be willing to do it for free. Then, maybe contact the local colleges to see if there are any students who would do it for a charge (that might be less than a professional) then just start calling photographers and give them the exact specifics of what you want/need them to do.
And like @theichibun said, the fact that they may get some exposure is not a draw to any professional. Professionals will charge whatever they want.
Either way, make sure you have a professionally signed contract with all of the specifics laid out in advance, even if you use someone who is willing to do it for free—to avoid any problems down the line.