Sorry you can't have any pets. That's a real bummer. I think life is so much better with pets.
Apparently kittens are very fragile until 12 weeks of age. The slightest infection / virus can be lethal. It was a big initial hit when we found them in the wall. They were frail and malnourished and in critical condition, so we rushed them to the vet where they had to administer subcutaneous fluids for all of them, do a full checkup, and keep them in their care for a bit until they were stable. Even then we lost one the first night.
Gerry was looking bad for a good 48 hours a week or two later. He was lethargic, wouldn't raise his head, let alone play, eat, or drink. We brought him to the regular vet during the day, and they said they couldn't find anything wrong with him and didn't want to do to many tests in risk of harming him more. He declined further and we ended up having to go to the emergency vet in the middle of the night. Emergency fees are killer. They told us he probably had "fading kitten syndrome" and that there was nothing he could do, we just had to keep him warm and try to get food in him. We stayed up all night. I kept him in my shirt, and kept breathing in my shirt to keep him warmed up. We also force fed and force hydrated him. He bounced back some time the next day.
Curly had a similar scenario, but we caught it really early on. We noticed something was off with her and brought her to the vet immediately. They took a look at her and told us that she's completely fine and we were overreacting. She declined further when we went home. We took her back again, and still they couldn't find anything. She got really bad that night and we brought her back a third time. Finally they saw it and started doing tests. Unfortunately, they had to run the gamut of tests to figure it out - temperature, eye exam, fecal, blood test #1, blood test #2, etc. Nothing was conclusive, but something had to be done, or we were going to lose her. They decided to take the "shotgun approach" and just administer several types of treatment, hoping one of them worked. Needless to say, it wasn't a cheap approach. One of the things they did was give her a fever reducer. Afterwards, we did the same thing with her, as we did with Gerry and stayed up all night with her. We brought her back to the vet the next morning (as instructed) and the fever was creeping back up. They told us to leave her with them so they could monitor throughout the day. They did, and gave her another fever reducer before she left and told us to bring her back again the next day. We did and they watched her all day again. This happened for one more day still, when finally the fever broke. They don't know what the problem was, but it was resolved, after a LOT of care.
We've had a few other smaller vet visits. We've had to get flea medication, which is quite expensive (they had fleas when we found them), we had to deworm them and treat them for coccidia. we've needed to buy antivirals and antibiotics. We've had to buy several bottles (they kept chewing through the nipples) and syringes. Newborn kittens require formula, which is really expensive too. After that, they require a very specific type of young kitten food, which is also not cheap. We spent a lot of money on training pads while they were being litter trained, and we had to buy a special kind of litter that wouldn't harm them if they ate it (and they did) while being trained. Their shots are coming up and they're each going to need three rounds of shots. It is also coming time to test them for FIV and Leukemia.
To add onto it, we lost some time at work while caring for the kittens when they were in critical condition, so we lost some of our salaries. I'm so thankful that I had saved up an emergency fund (well, not really saved up. I took out some extra student loans). Otherwise, we wouldn't have been able to save them. Unfortunately, those funds are about gone now and we're living on students' salaries. That's about where we stand, now, and why we're asking for help.