Most people call us because of what they notice upstairs. The house smells musty after rain, the floors feel cold or damp, or the AC tech came out from under the house and mentioned water. Bare dirt under a raised house gives off moisture all the time, and in a vented crawl space it rises right into the framing, which is what a ground cover is there to stop.
The price turns on how big the crawl space is, how low it is to work in, how much junk or old insulation has to come out first, and whether a leak needs fixing before any plastic goes down. Choosing a plain ground cover or a fully sealed crawl space moves it the most. The schedule mostly waits on that water repair and the permit check, and the written estimate spells out both.
One rule to know before you hire anyone. In Louisiana, a home improvement job over $7,500 and up to $50,000 has to be bid or done by a registered home improvement contractor or a licensed contractor, so ask whoever quotes you which one they are.