I hesitate to buy anything that has mold or visible mildew that is mechanical (from experience). Check the underside of the machine for rust, and the bobbin casing. Feel the bobbin casing for unevenness, pitting from dampness can drive the stitching length insane. If you have an area that you can bleach out the mold in the wood, and the machine has no rust, then $20 is a little investment. But do not bring it into your house, mold spores are like fruit flies looking for fruit.