I started my young life as a yacht painter in my grandfather's boat shop at 12 and have been painting and house building all my life. We built boats of wood because we had nothing better, we built homes of wood because we had nothing better. I grew up putting wood siding (cedar, redwood) on houses, it was the best we had. Now I tell people use cement siding, paint it once every thirty years if it needs it or not.
Some contractors work on time and material others on a firm contract. I would never hire the former and am leary of the latter. A contractor may low-ball a bid to get the job planning to make a killing on change orders. If you say good morning to them, they charge you extra for that. If the contract is not very, very specific and extensively fleshed out or if they display their change order schedule prominently on top, show them the door.