I need to know the average price of a Level 1, or Phase 1 commercial prop appreaisal?

I am thinking about purchasing a warehouse that was formerly a paint manufacturing company. I was advised that I could very well need a Level 1/Phase 1...or a Level 2/Phase 2 Commerical Property Appraisal, first. Could someone explain these to me, and tell me about what one would run? Thanks!!