My day job is at a machine dealership. We sell Viking-Husqvarna machines and we service all makes and models. I would stay away from any Singers manufactured after 1988 - 89, which is when the company changed hands. If you can locate a good, mechanical solidly-built older machine, it should be good. However, they don't always come with all of the attachments. If you purchase a new machine from a good dealership, inquire to see if they offer a service warranty and any "Get-Up-and-Running" lessons, complimentary.
I've toyed with the idea of obtaining a used industrial machine but when I'm running bone casings, I find that slow and steady wins the race, and don't think I'd have as much control on an industrial, even though they go through everything. To scratch that particular itch, I purchased a working, refurbished treadle machine from about 1900. But to be honest, I use my new, computerized machine with speed control most often. (That may balance out as I gain more control with the treadle.)
I don't know what area of the world you are from, so I can't recommend brands specifically for you. I do know that in my area, in the US, the top brands are Bernina, Janome (some still have metal foot controls, which I find preferable to Viking's plastic) Pfaff and Viking. In my experience, (theater & factory) I've often found that lower-end machines don't have the motor strength to get through much more than quilting cotton when it comes to multiple layers. Bring work with you to try out a machine. If the dealership or owner won't let you, move on.
The advice from the previous poster regarding testing out any machine from craig's list *before* your purchase it is solid. At our store, people sometimes don't want to fix their older machines, due to the cost involved, and they will unload them on CL. You could end up with a $20 door stop that needs $200 or more worth of work, or worse, simply cannot be fixed for whatever reason - destroyed wiring, fire/flood damage, or parts no longer available. (I've seen it all.)
On the other hand, you could end up with a sweet working antique for $200 with it's original attachments. My guess is, if you sew, you'll know. Trust your gut. Also, perhaps you have a family member or friend willing to let a machine go. Sometimes a treasure is sitting in a closet because the owner hates to sew.