Will steel angle work for a decent machine?

[Jess]

and later modify the cnc to cut thin plate steel by getting a spindle etc later on

'Thin' makes me wonder if the requirement is for cutting out 2D/flat shapes, which might make a plasma cutter a viable option. It's often attractive because the lack of contact with the work piece means that the machine doesn't have to be nearly as rigid.

If there's a need for 'engraved' features on plasma cut work, then one option is to etch it with acid. If you've seen a brass and enamel sign, chances are it was produced this way. With very thin materials it's even possible to cut out shapes by etching from both sides. Etching is faster (specifically, it's great for area, but rubbish for depth) and cheaper than CNC but does involve some fairly nasty chemicals.

Yea, I think I will get into CAD before I lift a single tool, but first, I definitely need to do far more research

That CAD experience will pay off when you've got a CNC machine, and you need to prepare jobs for it.

If plasma cutting sounds like it might meet your requirements, BTW, then I think there's a few machine designs in the plasma table forum.