Fortunately my skids have taken care of that themselves, due to their preferences for illegal activities, and their behavior toward their dad and myself. Dad works in law enforcement, and I did also for many years, so when they CHOSE to move out to avoid house rules etc., then wanted to move back in because it was "easier", NOPE, NOT GONNA HAPPEN. My husband even called Dr. Laura and she advised him NOT to let them move back in, as once they have decided to be adults, they need to learn how to do it, and moving back in would allow them to be "kids" again. Also, I hope you all realize that even if your kids (or spouses kids) are 18 or over, as long as they live in your home, YOU and YOUR insurance company can be gone after to pay damages for their actions. We have a friend facing that now with his 18 year old son who stole a vehicle and wrecked it, and another aquaintance who almost lost everything when their 18 year old set a fire and destroyed a state park/buildings. I was paying ALL of my own bills at 17, and moved out and was totally self sufficient at 18, including paying my own way through college. I never asked my parents for a thing. My education could be financed, their retirement couldn't. My husband knows that the best thing he can do for his "children" now is provide love, guidance when asked, and make them accountable for their own actions/life. THANK GOODNESS my husband grew a pair over the last couple of years!

Why are they wanting to move back? If its to help them I'd set up deadlines and goals so they know they need to save money, get a job, find an apartment, or whatever the reason they need to move back. I wouldn't leave it open ended as how long they can stay or it'll end up way longer than you want and end in a fight.
I don't think it's unreasonable to say " You can stay here six months and while saving money and/or looking for a job and we'll readdress it in six months if you still can't move" as long as they respect you and your home. But saying "Yes you can move back in" with no deadline isn't good, but I don't know your situation or why they want to move in with you.

My BD and my SS, both 22 at the time, moved in with DH and me. BD had broken up with a loser boyfriend and she needed someplace to be safe and to get her head together. SS moved in because, as it turns out, it was easier to do drugs than go to school and have a job. Everyone but DH eventually figured this out. Having them both there at the same time was awful, especially since DH and I married after we thought they were safely out of the house.

We made the mistake of not having clear expectations and an exit plan for them. BD eventually went back to school and worked part time, and once she did that I co-signed a lease on an apartment. SS eventually left to go to school out of state, which turned into more drugs and no school. Lots of drama, which led me to Steptalk. BTW, SS has been clean for about 6 months and we're hopeful for him.

Should either one need to move back in ("want to" move back in is not an option), believe me we will have written expectations.

I am an adult skid (now SM). When I moved out... my parents took the FLOOR out of my room to "fix" it... twelve years later my old room STILL dosn't have a floor. If that tells you what length my parents went too LOL!

I hear that! My two little sisters shared a room, so when I moved out, they each had their own room and were not giving that up! Besides, it was a matter of pride that would have kept me from even asking to move back in. There were many times that I lived on peanut butter crackers, but there was no way I would let my parents think that I failed at making it on my own.

When I was a teen I felt like I should be out of my parents' house as soon as I turned 18. It really bothered me that I turned 18 in July and had to stay at my parents' house until that September when I went to college. And my parents are both my bio-parents - i.e., no step involved!

I can't imagine ever WANTING to move back, unless it was to help them financially during their retirement or something.

My BIL is 32 and STILL living in my MIL's basement. I don't understand how kids want to stay like that!!

I'm still dealing with this right now. My advice is to NOT let them move back in under any circumstances. My SS34 moved in in April. He didn't look for work, laid around watching tv and playing video games. Ate everything in the house. And was a total slob. He never disrepected me verbally but I felt the disrespect everytime he whined about things and left messes everywhere. I felt that if I were ever in his position, I would bust my ass to make sure the place was spotless, empty the dishwasher, clean my bathroom, etc. Those things never happen until I specifially ask him to do things. He does them, but half assed if you know what I mean.
Then we had the joy of my BD29 moving in for the summer at the same time because she lost her job. First off, he developed a crush on her and hit on her all the time. EEEEWWWWWW. Then he got pissed off because we gave her the spare room because she was paying rent. Then because of his behavior, she started getting sloppier and would stay out all night at friends to avoid him.
We finally gave them deadlines. Her's is Friday!!! She is back at school full time and has a nice little place. He has worked since June and has only saved a little because we made him. He is still a pig and hasn't even started looking for anything since he has to be gone in a month.
This has driven me into counceling and put a lot of strain on my marriage. DH and I have agreed, no one will live with us again under any circumstances. We'll see if he can keep his word on that one.
If you HAVE to do this, sit down with all adults and have a written agreement. If they break it, they should be put out of the house.

Caveat - I know that I'm not typical on this site!

Since we're the long-distance NCPs, it's not a matter of SD moving "back" in, but we do plan on inviting SD14 to live with us after high school.

There WILL be a contract though. "Rent" paid, basic house rules, etc. If SD fails out or decides not to go to school, she'll have 90 days to get a job and gtfo.

At this time, we're comfortable with the idea because SD14 is a good kid. We haven't told her what we're thinking, and won't until after her junior year, so there have been no promises made. If her behavior changes in the next three years, the offer won't be made.

DH struck out on his own at 19, and is of the firm belief that kids need to grow up and that sometimes it takes a boot in the butt. We're pushing BM to give SD14 more responsibility like paying for her won cell phone, or getting a checking account so she can learn to manage her own money, but BM doesn't want to go to the effort.