I live in Louisiana and recently found an ad for some cypress boards that had been salvaged from some really old houses. I was just curious as to whether or not this wood is worthy of lutherie. Back? Sides? Neck? Any thoughts on this?
No reason why you can't use it for back & sides.
It's used a lot for flamenco guitars originally because it was cheep,
now unfortunately getting rather expensive but has a wonderful aroma that lasts for years.
Look for 2X10 or wider boards with a big portion of the pith in the center. Either side of the pith will be mostly quartered and can be resawn at an angle to acheive 90 degree grain. I have some old growth sinker Cypress with super dense growth ring counts, pulled out of the basin by Henderson but have not considered using it for an instrument until your threads here and on OLF.