I reasonable amount can be deducted as contract labor...Cash payments to contracted friends, relatives, a neighbor etc.
Don't forget all those labor receipts that were misplaced to various subcontractors.
Many contractors work cheaper for payment in Greenbacks. They will scribble a receipt which is meaningless on their end. All it takes is a letter head.
Costs of DIY improvements could run as high as 80% of contracted work and as cheap as 50% on most jobs requiring both material and labor.
Reasoning: You pay more on retail costs for your material, and you put in more hours due to non professional labor.
When I built I was fortunate enough to find a young plumber/entrepreneur who was trying to establish credit with suppliers. Credit with his suppliers was established through initial cash orders first and then from there he was given...30days...60days...credit. He told me buy what you want thru my business and pay cash upfront at my contractors prices. My furnace, bath, and kitchen fixtures/appliances were purchased and he established 30 day credit needed for his new company. It was a win/win for both of us.
nitetrak