I bought a used Brother 1034d a fe years ago from Craigslist. I had it tuned up by my sewing machine guy. Then was fortunate to find a serger class at a not so LQS. I have probably $150 into the machine total. It is 4 thread with differential feed. I'm very happy I went the route I did. The tip we were given re threading is simply tie newvthread to old and pull it through....in order of course. And the other great tip is when you are doing a particular task, write down your various settings for each task. Eliminates all the fiddling if you don't use the machine much.