How to Care for Pet Mice
Mice are intelligent and active creatures that are just as gentle and loving as cats and dogs. If you’re planning to care for a mouse for the first time, you should get a pair because they usually need company, but do not keep two male mice together because they’d end up fighting. A pair of male and female mice, however, tend to produce babies every three weeks, so you should also avoid this.
Make sure that the mouse doesn’t have any diseases and was bred by a legitimate mouse breeder.
Here are some points to remember when raising mice as pets.

Housing for Mice
Mice should be kept in 60 cm x 50 cm x 30 cm wire cage with plastic flooring or a 10-gallon aquarium for a pair of mice. The top of the enclosure must have a screen lid that is securely placed on top. Place shredded paper and dust-extracted bedding on the floor, but do not use cedar shavings. The bedding must be cleaned weekly because they urinate and defecate on these.
Do not place the cage or aquarium near draughts, bright lights, or direct heat from sunlight and sources of heat. The temperature in the enclosure should be between 65° to 75° F.

Provide exercise toys such a solid plastic wheel (avoid the wire wheel), cardboard rolls, shredded paper towels, fruit wood for chewing, and hemp rope for climbing.
Diet and Nutrition
Mice are active creatures, that is why they need calories to burn off. Commercial food like seed mix, pellets, and lab blocks should be supplemented with apple, carrots, broccoli, blueberries, and a floret of cauliflower. They are fed once a day at night, but if the mouse is pregnant, it will need supplements for extra calories. Place the food and water in ceramic bowls instead of plastic bowls outside of the cage.

They will also need hard treats like fruit branches and dog biscuits to chew on at least once a week.
Care and Diseases
Mice should be handled carefully by holding the base of the tail and lifting the back end gently by sliding the hand under the body. Children should not be allowed to handle the mice because they can get injured.

You do not need to bathe mice, but you can spot-clean them with warm soapy water if their coat gets dirty. What you need to clean regularly, however, is their bedding. Rinse the cage with soapy water once a week and change the bedding and toys regularly.
Fortunately, mice are not prone to diseases although some might develop mammary tumors and viral or bacterial infections. Usually these problems come with old age and can be avoided with proper feeding and housing.