I look at the square footage and cost of previous projects and compare that to this project. Today the electricity bids and central air bids came in those are as predicted. My stepson handled the initial meeting with the buyer. I signed though so it's my responsibility. Next time I want to do a contract which includes a budget plus 15% or more. What I will do is inflate the budget about $4000 and include a provision that the cost could be $5000 higher in the final price. If my projections are accurate the customer saves $9000 if not the home ends up costing $5000 more than expected.