For all our suppliers we use purchase order numbers, corresponding to an address.

It seems like an easy fix, look for a roofing supplier, visit their store and ask for their contractor calling card, some mom and pop usually leave some.

Are there any tips/tricks on saving on lumber costs from suppliers?

I found a supplier that supplies used appliances , but im looking for a supplier that supplies scratch and dent appliances. 

Who are the true WHOLESALE Cabinet Suppliers in Southern California?

@Lee Carrell  To find the roofer who will do it, call the local metal supplier for things like this.  

I buy HVAC direct through from a nationwide supplier.

There are some instances where you can find things like furnaces cheaper directly from suppliers, but by and large if you know what you want, and buy it when it's available, you can make out pretty well.  

You should have multiple contractors, closing attorneys, insurance agents, material suppliers and lenders.  

A big check from the government and a 20 year contract with EDF (national electricity supplier) for 20 years (fixed rate per kWh) and that gives you a better ROI than a 45 unit apartment in the ghetto.