Getting pet rats, need some tips?

i dont need any ew answers please! my mom grew up with pet rats and she loved them and said they were very smart, so me an my sister are each getting a rat. my mom trained all of her rats to come when she whistled, so i also need tips on training, grooming, and what supplies i will need. also, whats the BEST place to get them from? a pet store or breeder?