Look for a used HQ16. I bought mine in 2010, used, with frame, etc. It has worked very well. My husband cleans it for me every 18 months to 2 years. When he opens it up there is very little dust, except near the head and in the bobbin area. But that is where you would expect it to be! I've had no timing issues, and the other issues I've had are attributable to "operator error'.
Qualifying the suggestion to look for a used HQ16 - try before you buy. (That means that you would have to find one fairly local to you.) Take a quilt sandwich with you and spend some time testing it. Otherwise you have no idea what you are really getting.