There is so much good information and advice in this thread.
I have two sergers. An oldish one, SingerMerrittlock 14u44, and a less oldish one, Huskylock 936. White and black thread respectively. (Those seem to be the most needed in my sewing room right now. Both of them stay set up in my sewing room.) Neither of them thread themselves. The edge cutter is an integral part of the machine. NOTE: If you buy an older machine, make sure you can get replacement blades for the machine's cutter. They do wear and it is very easy to serge over a pin, cutting it in half and ruining a blade.
The manuals are very clear about how to thread the little darlings. It took a little time and effort to learn and sometimes, if I haven't used them for a while, relearn; but don't pass up a really fine serger becaused it challenged you to learn to thread it unless you are having vision difficulty.
I bought the Singer at Sam's eons ago. It has lived through the rough and tumble of summer tours with large drum corps. 120 marching brass and drum players, color guard, and two or three sets of original flags. It went though being in the corps sewing room for the tours I couldn't join. It did alterations, from scratch costumes, repairs, and finally the refurbishing of the marching uniforms. The Husky has not been asked to do that sort of duty. It makes slipcovers for the rv, clothes, repairs towels, makes doll clothes, draperies, etc. It was substantially more expensive than the Singer and has a number of fascinating features and purrs along just like the Singer. The Singer sews with 3 or 4 threads. The Husky with 3, 4, or 5 threads. The Singer is not computerized; the Husky is. I can service the Singer. The Husky benefits from a very occasional trip to the Husky service/cleaning center. Both of them serge beautifully.
Please let us know how your hunt turns out. Enjoy your serger. There are lots of books with suggestions and projects. And you can snag "how to" classes that will teach you new stuff and remind you about the things you have't used lately.
Pat