What lenses will you be shooting with? Specifically, what focal length?
This is actually your critical question.
Before I built my own home studio set up, I had someone stand against the wall, and I took a look with various lenses to see what I can shoot
full body shots: 50mm. 105mm for close up work.
I'd love to use the 105mm for full body, but it's not possible given how small the room is.
5x5 might allow you to do headshots with a 50mm but little else.
If however you're into Macro, you'll have plenty of room...
Because, the focal length will determine how much distance you need between your subject and you shoot. A small subject can have a small distance even with a big focal length. A big subject you might need big distance with a small focal length.
You might also be thinking, what about using a wide angle lens?
That will let you shoot closer to the subject, but will distort your subject
That's why you're better off with longer focal lengths for portraits.
In addition, to get that really nice black background you've probably seen, it's best if there's quite a bit of distance behind the model.
So, in summary, minibar it is