burbguy82 -
I can empathize with your conundrum to some degree. I have two kids; one's a go-getter and the other was a challenge to say the least. I say "was" because now that child is incredibly productive and hard working, but that wasn't the case in the teen years.
We drew the line quite early in life for them. We didn't give them anything; they had to earn it. Pay for chores around the house. No cell phone until they could afford the plan (we paid for the phones; they had to pay for the service). No cars until they could afford the insurance; not unlike the phones.
Each was told that they had to have a "plan" for their own lives at 18 after high-school. We would pay for college, trade schools, etc ... whatever they wanted to further their education. If they wanted to go into military service, we'd support that choice also. But living at home in the basement as some form of mutated parasitic slug was NOT an option.
One went to college and then grad school. Very successful; then and now.
The other struggled. Moved out, got into trouble, had life kicks in the gut. Bad choices resulted in bad consequences. But slowly, methodically, the dim light started to grow brighter. The "cause and effect" of life began to make sense. Whereas the mean ol' dad (me) was never to be trusted or believed, other adults who gave advice seemed to echo my teachings and so somehow, some way, the message began to sink in. This child who was a true drain on us emotionally and physically early on, now had started to turn life around. I recall a conversation with a person who actually ended up employing my child (unbeknownst to me at the time), stating what an excellent, motivated, brilliant person showed up to work every day. I was nearly floored; both proud and bewildered at the same time. Now, several years later, this same child is self-employed, doing well, and communicates with us willingly and semi-regularly. Not unlike a family-channel movie, life has turned out well.
My point is that sometimes you have to play the long game and make the adult decisions in your own life, and risk alienating the "child" to boost the "adult" in a person. Some folks will rise to the top merely as a means of self-directed achievement. Others need to understand that life isn't as easy as it looks on YT or FB.
Sadly, some kids never grow up, even with the best of guidance. Don't consider yourself a failure if, after years of proper teachings, your kid fails. I've seen it in my LEO career many times. Some kids won't transition into adulthood because too many other distractions get in the way, and pity/self-loathing seems easier than getting a job. Parents are to blame when they don't set rules or provide proper guardrails for development. But not all parents are to blame for wanton children; at times "you just can't fix stupid" (credit Ron White).
My advice is to draw a line and stick to it. Now is a better time than never. If you don't set the expectations and enforce them, growth is unlikely. And it's not going to be easy for you, either. It's tough to say no. It's hard to turn them away when they do stupid things.
If you lay down the law, and enforce expectations, there's no guarantee the kid will respond positively.
But if you don't make them grow up, there's a VERY high likelihood they won't ever mature on their own.
So, in all seriousness, I offer my life advice to you. Do the right thing. Even if it fails, at least you won't be the reason it failed and you can say you tried as best you were able. And it might just work out well in the end ... it did for us!
Hence, my long answer to your short question is this:
After they become 18, cut your kids off when they no longer are doing something positive to improve their own lives.