Sometimes people choose birds as pets thinking they are less hassle than a dog cat. Most people would know that the larger the bird, the longer the lifespan. Even a budgie can live to be 7 years, and there are budgies that have lived to 13 and ever older! To give you the idea, most pet birds require a serious if not lifetime commitment:
Cockatoos up to 60+ years
African Greys up to 60+ years
Cockatiel 12 to 20 years
Parakeets 7 to 18 years
Lovebirds 15 to 25 years
Canaries 10 to 15 years
Finches 5 to 10 years
Any pet bird needs to have a cage that is at least big enough for them to stretch and flap their wings without hitting the walls or any hanging toys. A good rule of thumb is, the bigger the better. The most important thing to watch for when buying a cage is that the spacing between the bars is appropriate. Not too wide for the bird to squeeze through and escape (or maybe worse: try to squeeze through and get stuck).
Birds bathe in water or saturate themselves with dust to care for their feathers (plumage). This applies to all sizes; from budgies who love splashing around in the sink to parrots who dive head first in a pool! Without proper bathing habits most birds will develop feather problems. You will be responsible for teaching your bird these good habits, if you decide to buy a young one.
It is hard to say anything sensible about bird food as there are so many species that require different nutrients. Rule of thumb is to get yourself educated. Make sure you are providing a balanced diet. The right diet will also ensure a healthy beak. Birds use their beaks as we use our thumbs. It is used for small tasks and large problems, from putting a single feather in its place to ferociously defending their territory. Specialized veterinary care for birds, e.g. for clipping beaks, is difficult to find. Check your local veterinarian to see if they can help or know of a specialist.