Not always. You need to set up a mouse tank first and it's gotta be big enough for them (mice need a ton of space to live properly, atleast 10 gal for a single mouse, and 20 for 4 or more). More than one male never works if there are female mice around, so one male per tank and as many females as you want. Also, might want to set up two tanks of females and swap the male around every month, because constantly breeding the same mice exhausts the mice, and they'll die on you in a few months if you do that.
Also a BIG warning here. If you're breeding even just 2 females at a time, you're gonna get a TON of pinks. I get 12 pinks per female every 3 weeks and that's WAY more than enough to feed my snakes.
Single mice will not live long, they'll get depressed, and if you introduce other mice to them, they won't get along (and I mean don't even think about getting them to breed). If a male mouse has been alone for a month and not played with at all for that time, he'll probably be haggard and die on you. They're social animals, they need constant interaction for them to stay healthy, otherwise they turn into fat lazy things that just sleep all day and bite you everytime you stick your hand near them.
Just to give you an idea of my setup, I have three 15 gal tanks, each one with 2 females, and I switch the male around every 3 weeks, which gives the females in the other two tanks about 6 weeks to rest in between litters which generates me 24 pinks every 3 weeks, or 8 pinks a week, which I usually let mature to fuzzies or hoppers. I have another 10 gal tank I keep two or three young ones in so they can grow and be the next breeding generation, the soonest I ever breed a female is 4 months, and by then, they're big and healthy mice. All of my mice give me at LEAST 12 pups a litter, and if they have more than that they usually end up eating a few. I feed my mice 50% grains and seeds, 25% kitten chow, and 25% miscellaneous table scraps, peanut butter, yogurt drops, meal worms, and other things. My female mice are the size of a young rat, they're figgin hooge. Also each tank has a wheel, a couple ropes and tons of tubes so they all get a lot of excersize.
The bad thing about mice is you need to check on them EVERYDAY, they need food everyday, water everyday, and you need to clean their tanks every week or more because they'll get REAL stinky if you don't. So, it's a lot of work, but if you have like 5 snakes, then it pretty worth it (plus they're fun to play with), for one snake it's just overkill.
-Lemur 6