A well-socialized cavy will purr when scratched behind the ears. Make sure to examine the body of each cavy you pick up. It should feel solid and heavy not skinny and light. If it is a smooth coat it should be glossy and whatever the variety, should have thick fur. Look at the eyes to make sure they are not runny and the rear end for signs of diarrhea.
Guinea pigs can live in hutches just like rabbits.
They may be purchased at a pet store or made from wood and chicken wire. Newspapers spread on the floor of the cage will catch droppings and urine. The cavy leaves much urine so is prepared to clean the cage often. Cavies like to have a perch in their cage and a good idea is to use a small cardboard box so he can crawl onto it. You can also cut a door so he can crawl into his little house.