I have my iTunes library on my iPad. My husband wants to set up a library on his iPhone. How can we do this without screwing up my library or losing it altogether?

I Have a iTunes library with approx. 3000 songs on it and my husband has an iPod that has his music. He wants to create a new library for his new iPhone. I would like to know if we can create a new library for him without effecting my library. And we don't want to sync my whole library to his phone. I am also afraid of losing my library. Is there a way to have 2 separate libraries for 2devices? if it's possible, how do you set it up on a Mac?