10 years or so ago, Columbia Sportswear and Patagonia came out with the zip-off leg nylon fishing pants to go along with their even more expensive fishing shirts. The copy cats came out with competing models quickly, and those in turn got to sale racks quickly, whereupon I bought 4 pair, at about 10 bucks each.
Mine have wide mesh underwear built in, but I bought sizing large enough that I could wear them with boxer briefs or without for wet wading. I would suggest the same, but size differences among product lines means you should try them on first to know the size is right.
They have held up just fine. They can be washed by soaking in a bucket of water with dish soap in your motel room and rinsed in the sink, then hung to dry quickly like others have said. And they are so thin the "sock tuck" does not create an annoying binding seam against your leg like jeans, which are also too uncomfortable in warm weather. Near perfect fishing equipment in my book.
As it gets colder the fleece pants are good to have.