Always remember, the model has the last word.

If you don't feel comfortable or safe, stop the session and leave.  You are never obligated to put yourself in a position where your well being is at risk.  Yes, there are people that will take advantage of you and it's up to you to prevent being in that situation and it's up to you to get out of it.

Play it safe, carry a cell phone and let people you know where you will be shooting.  Have somebody call and check up on you or call them halfway through the shoot.