This is my opinion. Free advice is worth what you paid.
I have a machine shop that I use to make money with. My goals are probably different than yours.
This is something you build up over time, you don't just (usually) stroke a check for 100 grand and have a killer machine shop overnight. It takes time, effort and patience for finding good equipment and tooling for the right money.
All of this is highly dependent on budget, space, and size of work. Obviously a 10" south bend isn't going to be able to turn 8" gearbox shafts with any degree if usefulness, but they are great for making small pins, bushings and shafts.
I would consider a 15" x 60" lathe, a 9"x 40" sized knee mill and a 20" drill press the bare minimum. Smaller lathes can be nice for small things, but small mills just are annoying. 20" drill presses are easy to come by and cheap.
All can be found for very reasonable prices here in the midwest.
I would strongly encourage you to look at smaller industrial grade machinery vs bigger home shop grade tools. In my experience, brands like Grizzly and Jet are made as cheaply as possible and targeted toward home shops. If you're willing to look a little harder, there's a TON of nice machines out there for not much more money.
For lathes, I would look very strongly at a 15" LeBlond regal or a Clausing Colchester. Both are industry proven, common and easy to run. They are new enough that you have modern conveniences and old enough that they aren't junk. OLD USA iron is sometimes more trouble than its worth. Soft ways, lack of spindle speeds, just plain wore out. Still, there are some gems out there if you know where to look.
There's a slew of really good Asian engine lathes out there for really good money. They are made by brands that make industrial equipment. ACRA, Birmingham, YAM, Mori Seiki, and Mazak. Generally speaking, Japan makes the best machine tools in the world right now. Lots of decent stuff made in Taiwan too.
For mills, I will always have a soft spot for Bridgeports. They are the standard by which all mills are judged. Even though they are flawed and have some bad design features. Look for a big "M" cast into the base, that indicates a Meehanite cast iron base, a desirable feature. ACRA is probably top of the heap as far as imports go, SHARP, Birmingham, Kent, and ACER are all pretty decent too.
I'd get as big of drill press with as slow of a spindle speed you can find. Reversible spindle is a plus. Clausing is the standard here.
BTW, it never ends. No matter how big your shop, and how much you have. My machine shop has 2 lathes, a mill and a drill press. I want at least 2 or 3 more manual lathes, and 1 or 2 more mills, a radial drill, and some grinding equipment. And then CNC stuff after that.