Adopting a cat

I am potentially adopting a cat but yesterday I found out the harmful effects that changing the litter box could have on the fetus. Of course I don't want to chance it but I was wondering if any of you have been in this situation and could give me some tips or advice? I really want to adopt this cat because he is a stray and I want to give him a good home. I live on the second floor of a three level apartment and the cat stays upstairs but I can tell the people who live up there just neglect him and it breaks my heart. I've found him outside multiple times freezing and scared to death. Please tell me there's some way I can still manage to keep him?!