There are two ways that Darby new home builders earn out of housing projects; the bidding method and the cost plus method. Most new home builders generally use the bidding method. With this approach, a builder will get quotations from his subcontractors or just use his judgment to arrive at a reasonable cost for the project. Typically, the price will include the plumbing, floorings, electrics, fees and much more. Afterwards, they will add their profit together with a contingency fee that is usually 10% of the overall cost. Contingency fees are included in case the project gets over budgeted. The total cost will be presented to the homeowner.