I take in strays and several of mine had a bad case of cat flu as kittens.
One of them is a great big hulking almost 2 year old now and is an absolute joy, he's cuddly, gentle with the kids and even dp has a massive soft spot for him.
He's had no recurrances yet, although he suffers a bit from acne but that's unrelated. the only time he's been to the vet since was for an infected absess on his back.
Another one i found at the side of the road, half starved and very unwell... his chest cleared quickly with some gentle care but the gunky eyes got very infected and he almost lost the right one... it took months but after a huge battle it cleared and he can see with it again now, although he still has a scar on the iris. He's a little bit wheezy at times but other than that he's a huge fluffy monstor of a cat and wants to be friends with everyone.
I made the choice with both of them not to vaccinate as apparently the vaccinations can trigger a relapse and i do have to be on the watch for wheeziness or signs of them being unwell but they are easily two of the most loving and rewarding cats i've ever come across.
Keep in mind, even a healthy kitten has the potential to rack up huge vets bils... they can get sick anytime or have accidents and if that fact would be prohibitive then i don't think you should get a cat at all. Future vets bills are just something you'll have to factor in, no matter how healthy the kitten is now.