Most barrel work is pretty easy. What really made it special at one time was that the guys doing it were inventing methods to do very simple things to a very high standard. They kept the tricks of the trade to themselves. But that is pretty much a thing of the past, there are many videos out there today that give you all you need to do barrel work on home projects. The bigger problem I find is tight access to tools and barrels at a reasonable price.
I had a hard time getting started because I could never find a reasonable machine at Busy Bee, which is about a mile from me. They sold lots of machines but they were not at the time in any kind of rational sequence I could detect. If they had one thing, the next one up or down in size would be totally different in operating processes and capacities. They don't seem to have a clue what the small shop guy wants.
In the end I decided on the South Bend range as having the best instruction; machines at a price; parts; videos, etc... I started looking on auction sites, and found good machines for as little as 200 dollars. I settled on a 9" long bed, and a 9 inch toolroom machine. Then I got a shot at an excellent heavy 10. I realize the machines are dinosaurs but they still turn out the parts at a home shop rate. I don't know what happens when all the old guys die, will anyone want this stuff? At the moment though you can use a lathe like this for several years and get back out for more than you paid, for the cost of a coat of paint.
I do think that you need to get a machine as soon as possible and just have at it. You will need to discover what kind of cuts work in your machine. Seeing what some other guy does on his set-up is only part of the story.
For threading I would look at a machine that has a threading dial, that can be one tiny money pit on a South Bend if it doesn't come with it. Or at least find a source for one. Also, change gears or a gear box are both fine for small scale work. Often guys who opted for the external gears didn't use the machine as much. Guys who bought the toolroom version had it in use every day. So it can be upside down world, where the cheaper machines are actually now the better ones. Also, stuff that is super expensive, like accessories, or tool room grade gear, doesn't get hardly any more money on the auction sites than stuff that isn't. You are looking 500-900 to get a good machine right away. With better contacts and more time you will get offers for totally awesome gear for as little as 200. I got offered a really great lathe and a two headed mill from a guy who owned a restoration shop, one was something the US army used, the other was some german mill similar to a Deckel. Either for 200. I had all my machines and no more space at the time...
Any time you see an oldie you wish you knew more about:
http://lathes.co.uk/