A scope written by trade, allowances stated in dollars, exclusions named, a schedule, payment tied to milestones, a written change-order process, haul-off and cleanup, and proof of insurance. A number on a page without those is a guess you cannot hold anyone to.
More detail
An estimate's job is to make the project comparable and enforceable, and eight elements do that work. Scope by trade: demolition, framing, plumbing, electrical, HVAC, drywall, tile, cabinets, counters, paint, each with what is and is not being done, so two bids can be compared line by line instead of total to total. Allowances in dollars: "cabinet allowance $6,000, tile allowance $8 per square foot" is checkable against what you actually pick; "quality finishes included" is not, and vague allowances are where lowball bids hide. Exclusions: the honest estimate names what it does not cover (the glass enclosure, the appliances, the surprise behind the wall) instead of letting you discover it. Schedule: sequence and duration, keyed to materials being on hand. Payment terms: tied to completed milestones, with a modest start payment; a contractor asking for half up front is financing themselves with your bathroom. Change orders: any scope change priced in writing and signed before the work happens, which protects both sides. The unglamorous line items: demolition haul-off, daily cleanup, floor and dust protection. And the paperwork that costs nothing to ask for: a certificate of insurance naming the job, and the licensed trade contractors identified for electrical, plumbing, and HVAC. Every estimate here ships with all eight, fixed-price, after a free walkthrough.