Can a catholic single mother receive communion?
To receive communion you have to be in state of grace. All sinners who confess are returned to this state, if their intention is not to sin again, regardless of whether they do or do not later on. A woman living with a man can be in the state of grace if she is not having sexual relations with him. This means she could be single, or divorced and still be able to go to communion. Even if she does have sex with him, but is repentant, confesses, and has the intention of abstaining from this (difficult, but possible) she is in a state of grace and can go to communion.
I know very few people who are designated Catholic who have never had First Communion. Wow! I’m really not sure where you’re coming from. I grew up Catholic in the 1940s and 50s. My oldest brother is an ordained deacon and an old-line sort. But he would not take the tack you are taking. Even in the oldest days, we were taught of a forgiving God. Today’s Church WANTS its members to make their peace and be included. I also must point out that neither you nor I know exactly why this question was asked. I am not trying to be insulting, but I am concerned about the image of Catholicism you are projecting.