To keep guinea pigs as pets you must consider their social grouping. In the wild they would live in family colonies and so as pets it is best to keep a pair together. Two adult males would most certainly end up fighting so best pairings would be a mother and daughter or a father and son.
They will need housing in either an outdoor hutch similar in size to a rabbit hutch with an exercise area or they can be kept in an indoor hutch with a portable hutch to be used outside. Which ever you choose, hutches should be cleaned out two or three times a week and then once a fortnight they should have a really thorough clean. One of the problems of keeping guinea pigs as pets is that they do have a habit of playing with their water bottles and this tends to soak their bedding material. Bedding should consist of a base layer of cat litter or wood chippings and then a good layer of straw on top. This should be renewed about three times a week. Because of their habit of playing with the water bottle, this should be topped up very often and also cleaned at least once a week to avoid algae. Food containers too should be washed thoroughly once a week.
As guinea pigs cannot synthesise their own Vitamin C, it is suggested that a Vitamin C tablet is dissolved in the drinking water. However, if you add green stuffs to their diet of grain mixes, commercial pellets and good quality hay, this supplement may not be necessary.
As for health problems, your vet is the best person to speak to but in general teeth and claws can become overgrown and need clipping by a professional. Other problems can be mites under the skin causing itching and scratching. Again, you will need to consult your vet. If you choose to have guinea pigs as pets do make sure you gain considerable knowledge on their care to make the best possible home for them.