Sugar gliders are very high maintenance pets. They require an enormous amount of attention and care, and they are very fickle little things.
Do not get a single glider - they have a huge amount of trouble living alone. Get two or more, or don't get any.
Your house will need to be thoroughly prepared for sugar gliders. They can fit in tiny spaces, climb on everything, and glide to the last places you'd imagine.
They chew wires, pee and poop everywhere, and knock stuff over left and right. Their diet requires live insects and grubs, and you'll probably end up with a bunch of renegade cricket escapees living in your house.
Their diet must be varied constantly, but any given glider will have its own tastes, and will reject foods it doesn't like. You need to have a constant supply of fruits, vegetables, and insects at all times, and you'll probably have to hand feed the gliders a significant portion of the time.
They are extremely grumpy during the daytime, and extremely active all night long. Expect to be the landing pad for endless glides. They will climb the highest object in the room, hop off, glide across the room, and land directly on top of you, while you are sleeping.
Most owners will make a sort of nesting bag out of fleece, and keep the gliders inside it while they are sleeping. With a drawstring, you can wear the bag around your neck. This is adorable and sweet, but it will quickly drive home the fact that gliders are absolutely unbearable during the daytime. If you so much as move the wrong way, they will grumble and grouse about it for several minutes. If you try to wake them, they will make you pay the price. They hate being woken up or disturbed while they are trying to sleep.
You need to find one of the very few veterinarians who actually know how to treat a sugar glider. Most vets have no idea how to handle tiny marsupials from Papua New Guinea. Expect to pay top dollar for medical care.
You will also have to shell out the bucks for nutritional supplements, because gliders are so finicky and stubborn about their food.
If and when a glider dies, you have to buy another one, because they die of loneliness. A solitary glider is a very unhappy glider, and will probably become a dead glider sooner than later.
There are also moral and ethical concerns regarding the owning of sugar gliders. They are not a very common species, and it is likely that a large portion of the gliders that end up in a pet shop have been trapped in the wild and shipped overseas. By purchasing a glider, you are making yourself complicit in the depopulation of wild gliders.
In short, you can't just ask people on this site what you need to consider before buying a glider. You need to buy some books on the subject and read them in their entirety. Bringing sugar gliders into your home is not a decision that should be taken lightly. You are considering making a decision that will require an enormous amount of time, money, effort, education, and lifestyle changes. An incredibly active nocturnal animal is a challenging pet to own, and gliders are even more demanding than most other animals.