I want a guinea pig but my mom hates rodents?

I already have a dog (almost 6) and 6 fish. Easy to take care of-- well for me. I recently saw a video of two guinea pigs getting baths and i fell in LOVE with them! They are super cute! I had 4 hamsters (not simultaneously) but she hates them now! I really want a guinea pig... I want to know the caring for them, price, and how to convince her?!