Subcontractor Company

Dear Friends,

We wanna Implement SAP in one of our subcontractors. But other than that product, this subcontractor produces another product in a normal way ( buy raw materials himself and sell it in market ). I wanted to create 2 different material type for raw materials.the first type for materials we send to him ( they are non-valuated) , the second type for materials he buy himself and pay for them ( valuated ) . Am I right? is there any other thing I forgot?

what should I do for common materials between 2 product?

thanks in advance