Home lead testing kits
The home lead testing kits are very accurate if used properly, but only spot check.  I buy these same kits in boxes of 50 for home inspections.  If you are concerned about widespread lead, you need to have an electronic scan dome by a pro.  This type of electronic camera can detect lead in walls, trim, interior or exterior and can cover an entire house in half an hour.  Costs vary, but 200 to 300 bucks is average in my area.  If you are only concerned with a small area or certain surfaces, the home test is fine. There is a technique to it, don't want to over simplify, but not hard if you read and follow the directions carefully.  Good luck