I have 2 a Juki industrial 644(15years old) and a Elna (3years) cover stitch only. Cover stitch does tee shirts and my grandkids pjs. Juki does so much. Only serviced 1 time. I keep it setup next to main machine so I can do quick things. Also I serge my quilt before I bind them. They bind so much easier and neatly.
I would ask what you want to do with the machine? Don't buy a Cadillac if you need a pickup. Also you need help learning the machine. What local shop sells a brand you could live with?