We got our cats from one of their shelters, they are 12 now though. I also know someone who does this job, fosters pregnant cats for them and looks after the litter. I have been round and cuddled many of the tiny kittens, so very very cute. I always leave wanting to take one with me .
It is voluntary although they provide all the food etc but you do need a separate room for them.
I'd love to do this at some point but this year probably isn't the best time for it because I'm finishing up my PhD and need to focus on that.
I'd love more details on how much I'd need to be home, whether the room the kittens are in needs to be completely off limits etc because I might be in a position to do it next year or for the late summer litter if I've finished my thesis on time.