You get one, it is likely to lure others in. I had tried sticky traps and snap traps with limited success, didn't get rid of mice in the house until I got the live trap and put calking/rubber cement in all the cracks and openings I could find around my house. I think it was an opening by the dryer vent they were coming through.

I baited the live trap with peanut butter caught like 7 mice overnight (I didn't count, just dumped them into the outside trash can on trash day). A week and a couple mice later, I was mouse free.