回複：他們有書麵合同（也就一兩張紙。看清楚價格。開工交工日期。材料（品種質量）。。。定金尾數

Thank you,MrsKwok. 

This project will be around $20,000. I am not able to pay him for cash.

One more question, should I put liability Waiver in the contractor? "If contractor is injured in the course of performing the specific work. Homeowner shall be exempt from liability for those injuries to the fullest extent allowed by law".

Many thanks...