If things are fine in terms of the geneal custody arrangements, why involve the courts. I think there’s been some very good advice here:
She has de facto custody, and does the major amount of care-giving. Absent a major improvement in dad’s situation, a court would probably approve that arrnagement, the longer it goes on the better for her. If he’s not asking for something, why go to court?
(Talk to a lawyer to be sure that the current arrangement, without legal custody basis, does not allow the father to just grab the kid on a whim and go for an extended tour of the country… That would be my concern; the other would be whether she would be dinged if she got a better offer far away and suddenly can’t move because the father tries to legally block it. Talk to a lawyer).
She should wean dad away from using her place. If when she decides to move on seriously, that’s going to be a little awkward. “Oh, ignore him, he’s my ex-lover. He’ll be gone in 5 hours…” Dad has to learn that “over” does not mean “using the rec room is OK, but not the bedroom”. It means “over”. He has a child, he can figure out what to do with the child with the resources HE owns.
I agree, unless she can pinpoint some specific reason why dad’s place is inappropriate, then she has no grounds to complain. The courts prevent kids getting into bad situations, not immature ones. Maybe it will be eye-opening for Junior to see how life works if you are a slacker with no money… Of course, he could always take the kid to the zoo or something, if he doesn’t want to show off his place.
The issue of support can always be used as a threat. He must make enough to pay the rent, hopefully from a legitimate job (if not, that’s a legitimate lever too). From what I know, he will be asked to produce tax returns and the court will assess support based on that. Then, some places have interesting threats if you fall behind - no drivers license, etc. If he’s erratic now, the question is - do you want to go to court and force him to pay, possibly get him into all kinds of trouble, or do you want to keep that threat as a future level if the custody gets ugly? “stop me from moving to Baltimore, and I will make sure your beer money goes to child support”.
My advice - talk to a lawyer, stop dad from stopping over.
Oh, and keep a journal (typical lawyer advice). Dates, times dad has custody. What they did. How much dad paid support, when. What the kid said about dad’s visit (liked it, boring, hot, cold, tired, good meal or just fries and chocolate?) No editorials, just facts with date time. Any threats or demands or outrageous requests. (“Can I borrow $60 to take him to the zoo?”) If/when it comes to court, the judge likes facts - about how involved and how good a parent Dad was.