Re bid if necessary

Dont accept so many changes that you end up doing a much more complicated or expensive job than you bid for. When you realize youre into new territory, stop work and draw up a re bid, showing the entire job as originally envisioned and overlay the scope of the new work. Let the client know it will cost $x more than the original bid to proceed. Its the clients decision how much to pay. How smart you want to be while youre working for them is your decision.