So i need a free api to handle this!
You do not; you do this locally on your own machine / server using the xpub. You will have one xpub per customer and derive as many addresses as you want fro that.
Unlimited addresses!
You can do that directly with the xpub.
No Expiration of those addresses!
Bitcoin addresses don't expire.
I don't want use some third party sites
Then don't use an API to derive addresses from xpub; just do it locally yourself, as I and BlackHatCoiner suggested.