so is there a standard rate to charge people or is that up to me, i dont wanto undercharge yet overcharge.
Totally up to you.
I've made a bunch of short films with zero payment. (Everyone knew that up front. That's important!)
My last project, everyone got paid... a mighty $75 per day. Many of them had put in time for $0 on previous projects of mine; it was just the right thing to do, when I had a semi-serious budget to work with.
You'll carry obligations, though. When you're asking people to do work for no compensation, there'll always be an unspoken reciprocal debt.
For example, the paid PA on my last shoot (who had also worked for nothing, as an actor for me, earlier) is now putting together his first film project. He's calling in all the favours he can think of... and yah, I'll be there for him. 'Cos he did me right back then, and it's the least I can do for him now.
One hand washes the other.
I guess it comes down to maintaining a circle.
Just don't get in a habit of milking people. *That* will come back to bite your butt, someday.
Long opinion short:
If you can pay even a token amount, go for it.
If you can't, that's no big worry, either. Just as long as everyone understands what the deal is.