Machine type
Overlock machines that trim the edge and wrap it in thread as they sew, with a differential feed for knits. Here that's JUKI's MO-654DE and Brother's 1034D, both household machines on household current. On a used one, check the knives cut cleanly, ask for a balanced 4-thread sample and a rolled hem, and make sure the converters and feet are included.
2 models we cover.
JUKI
Serger$150–$160 typical ask
1 on eBay
Brother
Serger$220–$320 typical ask
49 on eBay