Headlights on, engine off!!!!

Hi, My son who recently moved to Florida just bought a 1998 Chevy Prism from someone who I believe worked at a car dealership but was selling the car privately (first red flag). It "supposedly" has 82,000. miles on it and when my son test drove it everything seemed ok except some sort of problem with the blinker lights. After he purchased it for 2400. (he took 100. off to fix the blinker problem) my son was driving at night and when he turned the headlights on the car engine shut down!! Now he can't drive the car at night!! 3 quick questions---if anyone can help I would really appreciate it.
1. Do you have any recourse or lemon law type of warranty when buying privately??
2. Does this sound like an expensive repair and have you ever heard of such a thing?
3. Could the person selling the car have turned back the odometer?
Thanks so very much for your time and consideration.

looks like a short circuit somewhere. check the fuses and if you have a multimeter check the conductivity of cables to and from the headlights. Does it matter if you use high/vs low beams?
good luck!

http://www.automotiveforums.com/vbulletin/showthread.php?t=446242 I wouldn't be suprised if the grounding to the DRL module was at fault.