Weird symptoms in kitten

Hi guys, 

I recently rescued 3 kittens and I don't think I'm doing a great job (I know I can't afford to have pets but children were throwing stones at these kittens and I can't just leave them there). I am looking for families to adopt my kittens but, in this country there are only a handful of people who'd like to care for local breed cats.

Anyway, The third kitten (they were born December last year) showed weird symptoms last night. Suddenly she cannot stand and vomiting, her breathing was laborious and she'd just lie down (for hours). I thought she was dying and I stayed on her side and brought her out so she can see the sunlight before she passed on and then I rested for a while. When I went back to check on her, she was standing and asking for food (like nothing happened). It was a roller coaster of emotions and I am still very afraid for her. 

I know I should bring her to a vet, but I am in a tight situation right now, I can't even pay for my electricity bill and only have enough for food. Has anyone of you experienced this? I love her with all my heart but, I am very broke.

Can anyone please help? 

I don't know the common infectious diseases in your region. That degree of lethargy and increased effort breathing in a 4 month old cat is alarming. If she can't breathe well enough to oxygenate cells and feed organs with oxygenated blood, that degree of lethargy can be seen. How's her nose and sounds when breathing?  Noisy? Wet? Visible nasal or eye discharge?

If no gunk, no wet breathing, no discharge, and no raspy breathing or sneezing, deeper/internal factors causing lethargy are concerning. Heavy parasite load can lead to anemia and weakness. Dehydration makes them very weak, as does low blood glucose, making them "shocky."

Most problems that lead to lethargy need treatment, as they don't resolve on their own.

Give us a better idea of your observations of her, and feline disease/issues and parasitic disease endemic to your area. Few infectious diseases would cause the weakness you described in such a young cat, but not unheard of. She's too young for some diseases to cause symptoms yet, so that rules out a few causes. Respiratory infection and parasites are at the top of concerns for a kitten found outdoors without antibodies or deworming program in place yet.