My car is making a loud rattling, knocking noise after you crank and drive

I last changed the oil about 2000 miles ago, and it has just under 180,000 miles on it. I have had it for about 2 1/2 years and never had any other problems with it, and have definitely got my money’s worth out of it. The biggest problem I have is I have VERY limited money and can’t really afford to have it looked at if it is shot. I don’t really want to junk it if it is something that can be fixed for a decent price. If there are any other possibilities it could be, than I will get it checked out. Any ideas???