When I was 8 or 10 years old my Grandmother bought me a bicycle. I let a kid ride it and it got crunched. As I was sitting around forlorn my Grandmother imparted a bit of wisdom... she sez, "nobody values your stuff like you do, no one will take care of it the way you do and nobody else will suffer like you will if it gets broken."
That said, there's a select few with superior riding skills and experience that can have my bike keys whenever they need them. But the general rule is go buy your own.