We can only offer suggestions to you that on are on the cheap as you mentioned that you have no money. Someone posted about free tarps in your area. I would recommend getting some and some rope. Tie them down the side of the camper to the base. Where your vents and a/c are, cut holes for them. Then duct tape the tarps cut edge down around the bottom edge of those vents/ac. Go up the side of the vents as much as you can. It won't look pretty, but you are going to spend more money trying to fix a roof which sounds like it's not worth fixing in your situation, or that you will be able to afford.
As far as the gray tank goes, you can drop it down to get to the crack. Is the crack located at the top of the tank? Is it leaking when it's full?Anyway to by just open the gray tank valve and let it dump into the sewer or are you having to tote it away?
Is there any possible way for you to move back out of town and live with family until your housing situation gets fixed? I agree with the other, there is no way I would want to be in a trailer like that, especially for 6 months over the summer.
