I would whole-heartedly agree with everyone else's comment on this. Portraiture is not about some holy grail of lenses. It is about control of light, understanding of depth of field, understanding of circle of confusion, and posing/composition.
You can have the most expensive f0.70 lens you can find and get horrible bokeh. You can get the sharpest lens and have horrible detail. And the best equipment will still yield generic snapshots without controlling the highlights & shadows and posing/composing a shot that draws the viewer's eye at the proper point of attention.
I've shot thousands of portraits when I shot people. I've used the 110FE, 180CFe, 100CF, Canon 70-200, Canon 100L, 150HC, 100HC, etc. I never look at the "quality" of the lens, but rather that it'll fulfill requirements like working distance, depth of field, depth of focus, and flash sync. Sometimes, a lens too sharp is detrimental to the image.
You'd be better off just getting a proper, affordable lens, no matter what generation or "quality", and concentrate on spending your money on lighting and modifiers (whether that be studio lighting or something as simple as reflectors or an old Vivitar 285). Then, practice, practice, practice until you've learned the intricate details of that setup. Don't go longing for any different gear until you've found some limitation that you can't get over. You'll probably find that it's not the lens you are needing to upgrade!
While manual focus can definitely be used without any issue, the convenience of having working, proper AF is one less thing to pay attention to while learning your gear.
Yeah, it's not my money, so do as you wish. But you'd be better served putting that money into more important things!