Hello there!
Nice to hear from you again! Well, that was the only point where I used paid assets. I can share a link with you:
https://assetstore.unity.com/?q=3drt%20real%20people&orderBy=1 real people packages from 3DRT,
but at that time, he also had 90% discounts on his website for the same packs:
https://3drt.com/store/characters/humans/
https://3drt.com/store/characters/realpeople-kids-girls.html
https://3drt.com/store/characters/realpeople-seniors.html
https://3drt.com/store/characters/realpeople-females.html
https://3drt.com/store/characters/realpeople-males.html
etc., so I bought them all. I can model, but people are quite hard to design, and they should look appealing in comparison to environmental objects. So, yeah.
They're already UV-edited quite well, so it was easy to edit some default textures (for instance, to make the stewardess uniform and adjust to female characters model).
If I were doing it now again without buying assets, I would search for some low poly human-dummy models that are already UV-edited and try to make textures in Photoshop, applying some pictures of clothes and body parts I would search on Google (but of course, according to licensing rights).
Sorry if it wasn't much help.. Anyways, I am looking forward to playing your game. I will be waiting for its release!