How much milling are you proposing to do?
Vertical slides, and milling attachments are not as rigid as a milling machine.
Since milling cutters have teeth the cut will be interrupted, rather than the usual steady load imposed by straightforward turning.
Your choice of lathe, (And there will be no machine that is absolutely ideal), will be decided by what you want to do, the space, and budget available.
You won’t skim brake discs in a C1 lathe anymore than a machine capable of swinging 12″ will be ideal for watchmaking.
So think very carefully, research, and take advice, before purchasing. If in any doubt, buy a lathe that is a little larger than you think; your horizons will expand once you find just how useful a lathe is.
Before buying a pre-owned machine, definitely take someone with you to check it out before making a decision. If you don’t, you could be in for a lot of heartache, and expense!
having made your purchase, buy some books about lathework, learn how to sharpen and set cutting tools, and then just cut metal to gain experience. Then having acquired a little skill and familiarity with the machine, make a few simple tools. You will learn, gain confidence and experience and have small tools that will be useful in the future.
If you launch into making something complicated like a loco or a road engine, too soon, you are likely to be disappointed and out of pocket, and deprive yourself of a lot of pleasure.
Learn how to stand up, then to walk, before entering any sprints or marathons!
No one became a skilled turner in the first month, or even year!
Howard