I was once in your shoes. Contemplating the pros and cons of building my own rifles to save time and money from buying new custom rifles. 12 years later and literally over $200k in investment (when factoring in labor hours missed while learning), I don't regret it. I now have a shop with 3 lathes, soon to be two mills, an apprentice, and teaching classes for people like yourself.
All that being said, I WOULD HIGHLY RECOMMEND you look long and hard about whether you want to do this professionally, as a second career, or just a tinker hobby shop for yourself. If it is the latter, have at it but know that it is a lot of time, energy, money, learning, and failing before you put out consistent results.
I started with a Grizzly lathe, I wouldn't do it again for all the money in the world. Not that they don't work, but I just would rather buy once, cry once. The Clausing 8027J is a stud of a lathe, after that the higher end Taiwan lathers like the Sharp or Acra 1340 variable speed lathes are great. If money is no object, learn to write g-code and go with a Haas TL 1.
Don't get discouraged. It is a wonderful hobby/career and you can meet some amazing people. Especially in the older generations. I just did a repair job on a WW 2 era rifle and the 96 year old who commissioned it would sit by the door, drink coffee and tell amazing stories from various conflicts.
Chambering the rifle isn't a rough process but like others have said here...the work to get to running the reamer is the hard part. It took my apprentice over 4 hours to dial in his first barrel. He learned quickly what it meant to "chase the rabbit" on a .0005 indicator on a 5 groove barrel. Maybe it won't take you that long, or maybe it will take you longer, but you'll know the meaning of frustration when someone with years of knowledge does it in 10 minutes. But then, when you can do it in 10-15 min you'll look back and giggle at the simplicity of it. Learning the muscle memory and the feel in the hands just takes time.
Good luck !!!! We need more people in this wonderful profession