a friendly fee
A friendly fee is like a thank you note in cash so your friend doesn’t feel like they got taken advantage of when you use their stuff.
I borrowed my friend’s phone and gave him $5. He said I was the best friend he’d ever had.
I took my dad’s truck and left $20 on the hood. He said I was the most responsible son ever.
I borrowed my sister’s laptop and gave her $10. She said I was a total legend.
xs