Every platform carries lifetime consequences: range and cabin volume, completion feasibility, maintenance economics, and long-term value. The purchase agreement fixes most of them long before the first drawing is made, and gaps in the specification surface years later, on the completion floor, at full price.
Pre-owned airframes add a second layer: records, condition, and configuration history that reward the disciplined buyer and punish the hurried one. This phase decides how smooth every later phase will be.