If I may second Barb's comments.

I have five machines in my shop. 6 if you count the serger that my wife uses for her dolls.

Of those, the two industrial Pfaff machines, which were made in '63 and '68, are dedicated to Kiltmaking. One is a Janome 10001 embroidery maching for logos and special buttonholes. One is a 25 yr old Janome. One a 35 year old Bernina, and one is a 50 yr old singer.

All but the singer have knee lifts which I consider a neccessity.

Find an older, heavy basic machine. Check carefully for worn parts. Especially the needle bars. If worn, a needle bar will cause stitches to waver. It is the part that holds the needle and rides up and down in a race. This part is, if not the heart of a maching, the arms and legs, and the one thing which if worn will cost as much as a new machine to replace.
To check it, grasp the bar just above the needle and try to move it side to side, and front to back. Kinda like checking the wheel bearings on your car. If there is any movement, pass it by.

The second thing to check is the drive system. A strong motor will do no good if the drive is by a loose or worn belt or worn gears. (I prefer gears.)

You don't need fancy stitches. No electronics. Just a good old machine that does straight, zig-zag, and that has a foot that will lift as high as you can find. At least 1/2". There are times when your going to be sewing thru 8-12, or more, layers of fabric, and most machines won't lift the foot that high.

See if there is some old codger in your area that has been fixing machines for the last million years and sit with him over a cup of coffee. (you buy) He knows machines inside out and is far more knowlagable than the nice lady in the fancy quilting shop at the mall.

In fact stay away from any shop that has anything to do with quilting. Almost the entire sewing industry is in trouble today due to nobody sewing anymore.
Quilting is the newest fad. but Quilting machines are very light, very suited to women sewing one or two things during their "hobby" hours, and totally unsuited for what you will need. (I'm not knocking women or their "hobby' work. so please don't kill me for that last comment. It's that the two requirements for machines are completly different )