There are times when you know it's best to just turn and walk........examples I've had over the years:
when the rain is pouring through the back wall of the building
when there's no electricity / water / heating in the building
skidmarks on the bed
fleas hopping on the bed
put foot through stair tread while going upstairs
girl calls dealer as soon as you arrive
girl covered in a chicken-pox like rash (I got what was probably shingles a week later)
girl pissed out of her head
girl has more black teeth than white
the only entrance was via a back yard, which was an obstacle course of rubbish and old furniture
when an 18 year old chinese mutates into a 60 years old gremlin