What is your friend's budget?
Also, what does your friend do with the phone?
If your friend wants to pay the lowest price, tell them to buy the iPhone 7.
In my opinion it’s still a really good phone. It runs the latest version of iOS brilliantly, and (IMHO) is perfect for someone who wants to make calls/use the internet/send emails/send text/take photos (and isn’t going to be pixel peeping or obsesively concerned with image quality). No idea how long the 7 will receive updates; at a guess, it’ll get 1 (iOS 14) and potentially 2 (iOS 15). That being said, you can still use your phone after it’s stopped receiving official updates from Apple, just note that some apps may no longer be able to be updated/used with an older version of iOS.
If you want to play games, or do any picture/video rendering, the iPhone 8 would be a better choice. The more powerful CPU combined with a superior camera is a better combination (IMHO) compared to the 7.
Hope that helps!