General contracting means managing bigger, multi-phase jobs, often with subcontractors involved. The estimating and communication habits you build early matter more here than in almost any single-trade business.
Always include a contingency line, and say what it covers
A contingency of 5-15%, depending on project complexity, shown as its own line instead of folded into the total, signals to the customer that you have thought realistically about what could go wrong. It beats promising a number you will likely have to revise upward once work is underway.
Decide estimate vs quote deliberately, not by default
Use an estimate when hidden variables are genuinely likely: structural work, ground conditions, an older building with unknown wiring behind the walls. Use a quote for fixed-scope work like a single-room extension or a deck, where a confident fixed price is easier for a customer to compare against competitors.
Put your change-order policy in writing from the first estimate
On a multi-phase project, scope drifts constantly as a customer sees progress and starts wanting adjustments. A single line, "changes to scope will be billed separately and require written approval before work proceeds," turns that drift from a potential argument into a simple, expected process both sides already agreed to.
Label subcontractor pricing as an allowance, not a fixed number, whenever you have not yet confirmed the sub-trade's rate. "Electrical — allowance, subject to sub-contractor quote" protects you from being held to a figure that was really a placeholder.
Break estimates into phases customers can actually follow
Demolition, structure, and finishing as separate phases with their own line totals let a customer see where the money goes and where a project genuinely stands partway through. That is far more useful, and far less likely to trigger a dispute, than one large undifferentiated total for the whole job.
Vet subcontractors before you rely on their number
A subcontractor's quote is only as good as their track record for turning up and finishing on time, since their delay becomes your delay on the customer-facing timeline. Build a small bench of subcontractors you have actually worked with instead of sourcing a new one for every job. It protects the schedule you have promised far more than chasing the lowest sub-trade price each time.
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