I have an entry level Singer (Tempo 20). It's from the early 90's and only needed servicing a couple of years ago because it had got a bit furred up. I'm lucky to live in former mill town land, where the rag trade had a shop on every corner, and piece-work is still A Thing. It means I still have a haberdasher and a sewing machine service centre within walking distance. Entry level 30 years ago meant it can do everything up to light leathers,
lightweight canvas and denim, and nylon or polyester webbing for straps. However, it's plastic and not as robust as older machines. For basic outdoor stuff - simple roll top bag with light webbing straps for example, or the odd piece of clothing - it's fine. Just make sure you get the right needle for the material type you're sewing - leather, knitted, woven all need different tips.
I have a handcrank Singer 66K from about 1926 which will do nearly anything as long as it's not too thick for the foot to go over it, but it only does straight stitch and doesn't reverse. If you want a straight stitch it's the best I've seen, far better than my more modern machine. It can still be serviced, and you can still get the parts. It's made of cast iron.
I also have a cast iron Singer 29K46 Patcher, which is for leather - shoe repairs really - and has facilities you can't find on modern machines at all (360
o rotating foot whilst stitching!), but again it's not for heavy work (max leather is about 5-7mm in it), so collars, belts and handbags I hand stitch.
The questions I would be asking are: what are the jobs, what materials, what threads? If you want to make ordinary stuff such as clothing, then almost any 1950's, 60's or 70's 2nd hand decent machine with a recent service (more bang for your buck) would be my choice. Singer, Juki, Seiko, Durkopp Adler, Frister and Rossman, Brother will all do fine. If you're after doing heavier stuff (outdoor gear, canvas, webbing, straps etc) then you'll need a machine that's happy dealing with those materials - the phrase 'heavy duty' actually has meaning here! Again, I'd look for a 2nd hand heavy duty domestic, or commercial machine with a recent service. Check it has the correct feed for your materials (walking foot? roller foot?) fitted or available as a retrofit. Note that commercial machines frequently have separate motors which often run continuously, requiring you to learn a knee clutch operation. Other options are available, and modern ones can come with PWM speed controllers and all kinds of gearing. If you go down that road, you'll need space for the table and foot pedals - probably 1.2m by 60cm floor plan. I haven't the space...
I don't know where you're based, but
AlanSew in Machynlleth have machines and spares on ebay and I've bought parts from them in the past. I've never bought a machine from them, but they've been around long enough. If I were buying another machine, I'd be visiting my local shop
M&S Sewing and asking his advice - he has new and 2nd hand domestic and commercial machines, and he's my local service centre too.
For 'New' new machines, there's
College Sewing in Bury - I've bought spares from them in the past too.
Choice paralysis awaits you...