Got 2 cats from my mom, approx. 5-7 months old....?

My mom is something of an animal hoarder. We are trying to find homes for the animals because she is sick and is coming to live with us. These 2 cats/kittens are especially important to her for some reason. She is broke though, and to be honest, so are we. They are both close or at the age that they need to be neutered. We are not even sure if they have had shots. My mom has severe short term memory loss, and she can't remember which ones were vaccinated and which weren't. I suppose we should just ume that they aren't. We don't want to end up in a situation where they start marking and peeing all over our house before we can get them neutered. How should we handle this? Do they need to get vaccines before they can be neutered? One of the cats is always meowing and scratching at the door, so what could be going on with that? I'm finishing school this month and have a job lined up for September, so the money won't always be a problem. Right now, things are bad because we had to find a bigger place so my mother could come stay with us. So please, no telling me to get rid of the cats because we can't afford them. They make my mom happy, and that's something she needs right now, so I'll do what I have to.