Industrial machines are fabulous pieces of equipment. The speed , or stitches per minute can not be beat. But there are down sides and all industrial machines are not alike. Most industrial machines , it is not as easy to lower the feed dogs. They only straight stitch( most industrial) . Some require needles/bobbins not available at local sources. Many of the specialty feet do not interchange from domestic to industrial. They are very heavy , so removing it from the table for service can be an issue.
They are not cheap ! Many of the industrial machines that come available on Craigs list or other sources can be very difficult to find parts compatable to that machine. Always check if the table is included, so many are sold with just the machine head. Some are listed without the motor.
Check to see if you have a repair person who will take an industrial machine of the make you are considering.
The upside , is most will sew threw anything and the speed is unmatched. They are not complicated machines and maintainence is lower than the new computerized machines. Keep them oiled and clean and they run almost forever.