Design questions about purchasing a gut rehab w/ 203k

[Byron W.]

I'm looking to purchase a 3 unit property in Chicago that's a full gut rehab. Each unit is a 4 bedroom 1-1.5 bath. The property is currently gutted to the studs. I'm wondering, what should my plans be in terms of figuring out what size to make the rooms, bathroom, kitchen, etc? I would assume the GC would help decide those things but if he asks what size/layout I'd like everything to be, I wouldn't have a clue what to tell him. Should I look to hire a designer/architect for this? Or find a GC who has experience with creating the layouts for properties?

I've done various research on rehab loans but there seems to be very little information on this specific thing. This will be a live-in house hack, and my first property purchase.