The old cast iron machines are straight stitchers, some models had reverse lever before 1900. Singer gave their new model 201 a reverse lever in 1928 (ca), and updated their old model 15 with the same feature around the same time. You posted a picture of an early version 99, this model was given a reverse lever some time in the 1940s, at least in the US. If you happen to have a 99, remember you can always turn the fabric for reverse ;- ) . The Singer machines we get here are usually made in Scotland, and I have seen the backtack lever on the 99K from around 1950. The 99 is a 3/4 size machine, the 15, 66, 201 are some of Singers full size models.
There are a few Husqvarnas that were based on Singer's model 15, they were gradually developed and given reverse lever, feed dog drop on the bed, thread tension in front (in stead of on the side). The modifications were considered improvements and over the decades the differences became more distinct. Husqvarna 12 and CB-N turns up now and then, and about the same for Pfaff 30 and 31. There are a lot of old sewing machine brands.
Reliable old cars I'm not sure about, but the old cast iron straight stitchers generally are,, easy to give a DIY service and they have some advantages. When fixed up they will serve the owner a long time. Expect a bit of cleaning, oiling and tending too if you aquire one. I bought a 201K in a table and it has become a favorite. Some like hand cranks and treadles, but I have to admit, I bought one with light and motor and had it rewired. They will do the job in 2018 just as well as any, even better at times.
The cast iron models are all metal, gears, hinges, rods are made of hardened steel. It makes them very durable and most machines have very little wear. Almost all zigzaggers have plastic gears, and it is a bit more work to replace them if they are cracked or missing some teeth. If you find a Singer 401, it is an all metal zigzagger with various stitch patterns.
If you want to sew stiff, heavy leather and old type sail canvas you need an industrial model suitable for the job, but for most jobs you can get by with a domestic machine. Soft leather, sunbrella and the light polyester canvas types used today are no problem. It depends on what you are sewing, they behave very well with fine and sheer materials too.
The only thing they don't do is zigzag. There are buttonholers for them, blind hemmers, all kinds of accessories and even zigzag attachments. I keep a freearm zigzagger on the side, it's much easier. There are plenty of swing arm zigzag models from 1950 and up, only a few early models have stretchy stitches. By the early 50s nylon was the new thing, and a lot of models have some plastic gears. Some models like Berninas and Elnas are still very durable though and worth the effort of replacing a cracked gear. These are still some of the best and easy to use zigzagges.