Sounds like it could be hairballs. Many cats make different sounds when it comes to hairballs, so even if you've had another cat who had them you may not recognize it. My current cat sounded like she was trying to make bird calls, which I'd never seen before. But, after a trip to the vet, hairballs was the diagnosis. Please take him to a vet if you're able.

If money is a big issue, and you have no way to take him to a vet, you could try treating with hairball medicine on your own rather than do nothing. My cat loves a product called lax-aire. For the first week, I give it twice a day. See a vet first, though, if at all possible.