Selling friendship bracelets when you already gave some out for free?

[LOVE♥]

I did some for some people last year during the summer. A couple of my cousins asked for one. I would hate to ask for money, but I really need some way to buy more string if I'm going to continue making bracelets.
I was thinking about just giving away the ones people have already asked for, which is only like 2. Then possibly asking for money from then on? How would I go about doing that without being rude?
I love giving people things, so when someone asks my natural instinct is to just say yes and make them one.
How much should I charge?
A lot of the people who ask for them I don't think really have a paying job as far as I know. They're in their teens and living off of allowance. Or they are a college student and are trying to pay off loans. So it's another reason why I would hate to ask. :\
Oh, by the way, I don't go to public school so selling there isn't an option.
Oh, by the way, I don't go to public school so selling there isn't an option.