How many embryos? And what happens with the unused ones?

So I think we're really going to do IVF next cycle if this last IUI fails and I'm starting to get excited for it, but one thing is bothering me. How many healthy embryos did you ladies who have done this get? And then what happened with the ones you didn't use after you finally got pregnant? Did you throw them out or donate them or freeze when save them for possible future pregnancies? And if you did freeze them, what does is the storage fee like? Thanks!