It really doesn't cost that much. I started of with 2 males and two females. You will need to buy 3 set ups. First you will put them all in together and let them have at it. you will hear a lot of squeaking. after a bout 15 days, you will need to place the females in two separate setups. Approx 21 day after the first time they were together you should have two litters. The males will fight always so you might want to buy only one. Don't give them a wheel while you are trying to get them to breed, they are more likely to run than procreate. If you only want one litter at a time then only put one female in at a time. I would add the second one within 10 days so you don't have a big gap in litters though. your biggest expense will be mouse food, so I don't recommend top price mouse food unless you love them.