I do offer discounts on tile that the client orders thro' my distributor. I don't give it to them at my cost, that's my business, but I do give discount off retail.
I generally get cost of materials up front. The materials are the property of the client and the job and are stored on the premises. That way, if I get hit by a bus, they've got their materials and I may have enough money left in the bank to pay a carpenter to build a pine box.
I like John's idea of mud screeds, it may have never occured to me until I read his book. Just makes sense, doesn't it?