After months of looking around for affordable reclaimed flooring, we gave up the search and went with unfinished pine boards like the ones we used in the screen house. At $1.30/square foot, we haven't found any wood flooring that beats the price.
They're rather rough, with plenty of spots that need to be cut out. So, the first step was sorting them for the best boards we'll use in the most visible spots and the worst of the boards that will go under the bed and kitchen cabinets and in the closet. After they're all installed, we'll sand wherever needed and then stain all the boards.
We're nailing them down over an underlayment that adds another moisture barrier and accommodates any small variations of the subfloor. One row down, many to go. Luckily, we have a little extra help in town this week...