Haven't nurturing this idea of trading a Bitcoin in the near future,but one question that's always come as a concern to me is. Is proper for me to trust a friend of that high magnitude ?
People trading between other people without any form of intermediaries or centralized entities acting as a third party is the real peer to peer trading, also known as p2p.
If your friend is someone you completely trust and he (on the other hand trust you too) then why not, both of you can from time to time trade bitcoins without hassles, as long as you both are in agreement with your individually choosen exchange rate.
Like for example, I won't mention names, but I have some friends from this forum who I trade bitcoin with from time to time, we simply exchange bitcoin for fiat of usdt and vise viser when any of us are In the need of any this cryptocurrencies or fiat.
And most importantly, it will be interesting for you to note that this is the cheapest form of trading, since you won't be paying any fees, aside from the small amount the party sending the crypto will have to pay for blockchain transaction confirmation.