What is the appropriate cage size
Most people are going to agree that you cage needs to be at least 36x24x36 (lengthxwidthxheight) with no bigger than 1/2 inch bar spacing. Don't forget, bigger is always better!
One or Two or More?
Sugar Gliders are colony animals and do best in groups of two or more. A human cannot sleep in the pouch nor can they entertain such an active nocturnal animal at all times. Boredom CAN lead to depression which CAN lead to self mutilation.
What diet should I use?
No one is going to agree on this point, other than saying DO NOT use pellets as a main protein source. Sugar Gliders are sap sucking animals and derive most of their moisture from their foods and there is not enough moisture in a pellet to provide the needed water.
Do they need a vet?
Every animal needs veterinary care, including Sugar Gliders. They hide their illnesses and usually by the time they start showing that they are sick, they are REALLY sick. You need to establish a relationship with a glider knowledgeable vet before they have an emergency!