I just bought a new house. The inspector told me that the entry way paint is cracking because a previous owner painted over lead paint without using the proper primer. How do I find out which walls have lead paint before I move in? I plan on painting all the walls.
They make lead testing kits for this purpose.
You should ensure that you understand the correct process and procedures for painting over lead paint and that you take the proper safety precautions. The EPA has a website with lots of information on this.
Steven has given you the right info to test for lead. As a certified home inspector and licensed EPA Lead renovator, I question the method your inspector used to determine that there was lead paint present. He should have used a test swab for verifiable results. Assuming there is lead paint simply because over coated paint is cracking is making an irresponsible assumption. Any time a competent inspector is looking at a house built prior to 1978, he should random test, or offer to test for lead. Cracking paint can be caused by many situations. A few could be, cheap paint, paint applied over a very glossy paint that was not properly prepped, or even paint applied when temps were very hot and humidity very low causing paint to dry too fast. The primary reason could well be that the surface was not primed well, but that in itself is not a positive sign of lead paint underneath.
When you use the lead kit, be sure to follow the directions exactly. Use a utility knife to make a small "V" cut into the paint in an obscure area, being sure to expose a cross section of all layers of paint to the bare wood. The swabs are extremely sensitive and will pick up on very minute amounts of lead and give a red swap indication.
Do read some articles so you feel confident to use the lead tests properly. Simple testing is easy, but more extensive lead testing should be left to a pro. Good Luck