An initial "Well bird" vet visit tends to run $200 - $300, as they like to do a blood test to make sure the bird is free of any disease that would be hard to find just be examination. Birds are great at hiding illness. I haven't had Kiwi that long, but blood tests are recommended once a year and that's what I plan to do.

Definitely find a good avian vet before you get a bird. I went through two before I found one I liked.

As far as one bird or multiple...well, what kind of bird? For parakeets, I strongly recommend a pair. For lovebirds or parrotlets, a single bird. I agree with Giselle about lovebirds tending to be more aggressive than other small species, and parrotlets are pretty feisty as well. I have zero experience with cockatiels, but there are a LOT of 'tiels here on PT so I'm sure you wll have plenty of info available.

From the birds I have experience with, I would suggest a pair of english budgies. They're larger than the regular budgies, a bit heavier set, and in my experience they tame down easier, and are a lot cuddlier.

Gender is a topic I find debated a lot...I feel that as a general rule, male birds prefer women and female birds prefer men. This applies more to larger birds, although Kiwi has a definite preference for the ladies!

That cockatiel started kit you linked to is a lovely size for a pair of budgies, but I think it's not wide enough for a cockatiel. You probably already know this, but horizontal space is much more important than vertical space to keep our featherkids happy.

Keep the questions coming, I know all of the bird lovers here love talking about their Fids. ^_^