All together, I've accumulated six sergers - I think the "newest" one is a Husqvarna Huskylock 905.
If there is a lever to help with threading the upper (I think) looper - it makes the threading much easier.
My very old BabyLock and Pfaff Hobbylock do not have that - and those two are - at times - very c-h-a-l-l-e-n-g-i-n-g to thread. A tip that has helped a lot. - I put fray check on the end of the thread to stiffen it up a bit - and that helps quite a bit with the threading.
I paid less than $50 each for three of them.