Teenagers are tough. My kids are teens now and I feel like I'm never going to know if I'm doing the right thing. I guess in another 10 years we'll know.
A youth counselor I've listened to says "rules without relationship equals rebellion". I think that boundaries are VERY important. They are very important. The problem is that many people (more men than women) bark orders at their kids thinking they should just automatically obey. But if our kids only hear us barking orders and not talking with them and affriming them when they do good things and show maturity then they don't want to do the things we ask or tell them to do.
I've found with my daughter that when she understands the "whys" of our rules and boundaries she's better - but still fresh. I expect my teens to be fresh and slam doors and yell back. But they also know there will be consequences to those actions. My daughter knows that when she yells back or slams a door or does something disrespectful - particularly in front of others - that she loses privileges. The big things with her are her cell phone and the internet. In another year or so it will be the car. We tell her that those things are privileges and privileges come with responsibility.
We tell our kids that we expect that they will increase in responsibility and maturity - and as long as we see those increasing they will get increased privileges. But when there are rebellious set-backs and times when they intentionally disobey then they lose their cell phone or internet access or xbox - or whatever it is they they really want.
But, the other side of the coin is that we are very conscious of making a point of telling our kids when we are proud of them and when they do something good and/or responsible. My daughter will remind me when she wants to do something - she'll say mom you always say that privileges are based on us being responsible and you told me how well I've been doing and how proud you are of my increased maturity - so you should let me go to this party. And she's right - so we let out the "leash" a little bit and give her the opportunity to show her maturity. This last weekend we let her go to a party and required that she call us at a certain time and that she be home by a certain time. (She's 15 so the times are still pretty early.) She did both so next time we'll let her try it out again. But I know the time will come when she won't be home on time or she won't call when she's supposed to - and that will be a set-back and she'll lose some privilege. I won't be surprised and I won't take it personally - it's all part of the maturing process.
Your son in 18 and he's now able to be out on his own. you told him "your house - your rules" which is perfectly understandable. Wehn he's prepared to be mature and take his job seriously and follow the household boundaries then he can come back home. He probably will because he'll discover that being out on his own is no easy thing. But if he wants to experiment being out on his own make sure he's really on his own - his own car insurance, his own cell phone bill, etc. We tell out kids that as long as we are financing their life they are responsible to us. When they are able to finance their own life they can do whatever they want.
When your son wants to come back home allow him to do so with open arms - but be cretain that he understand the boundaries. Make sure that he understands that he must follow curfew and be willing to discuss curfew time - tell him that as you see increased responsibility with his job and when he is able to get to work on time every morning then his curfew can be relaxed, etc. At 18 he does need to have some input in to decisions regarding his life - but as long as you finance his life you still have the final say.
Good luck mama! I know since my kids are still in their early teens that this teenage stuff will continue to get harder. But I'm clining to the hope that they get better around 20 - I am looking forward to those days!!!