RetireJapan

I have tried searching for various versions of second-hand shops:
リサイクルショップ
質屋
中古
etc

Specifically for finding a decent price on a used iPhone (Japan version 7 or later). I have also looked at Treasure Factories and 2nd Streets, but surprisingly the prices seem to be equal to buying a new iPhone 8 directly from Apple. Perhaps this is just the way Japan prices their second-hand goods. But to be safe I wanted to reach out and ask if anyone had any good suggestions (not craigslist or FB scams, ha) on locations to check out. Currently based in Tokyo, Setagaya area.

I'm not sure why anyone would risk buying second-hand electricals / devices. You might end up with a piece of junk you have to chuck out after a couple of days.

Mercari

I'm a nerd and I really wanted the Softbank Star Wars phone, but I'm not on Softbank and there weren't any new ones available anywhere online. So, I ended up getting one of Mercari. It was a risk, but it turned out OK for me. The phone gets stuck sometimes playing Pokemon GO, but that might just be the game, not the phone.

Any specific phone version you are looking for?

I have a friend who has a iPhone repair business and also sells Second Hand iPhones. I can find out for you.

PM me details