Please help me ? I have an eighteen year old step-son, who also is likely bi-polar. What can motivate a lazy selfish, self-obsessed child to no seek immediate gratification with alcohol, sex, drugs and the nastiest music, friends, activities, homies he can find ?
Monday to Friday he is working 6 hours a day, relatively controlled and somewhat inter-active, then Friday, payday he goes out of control, back to biological family and nasty, uncontrolled, mean, disgusting, "whatever he can find."
If I can come up with rewards and punishments to re-direct, bad choices, I hope to adjust my step-son to be able to better control himself------i need help-------please help me ?

18 is an adult, not a child. Even if Aspergers and bipolar. (I'm really puzzled by the first diagnosis, which doesn't seem to fit his lifestyle. I worry that it is the diagnosis du jour.) One solution is to charge RENT. It's time he starting facing some realities of adulthood. That will cramp his ability to get booze and drugs if not the rest of it too.

I will agree, he is now a adult, not a child. And needs to be treated as such. Rent, pay for his own things, cell phone, clothes and more.

Who is doing his laundry, does he have car, or if he uses public transit, who is paying for all of it.

You have house rules and he is required to follow them.

At eight or eighty an adult is one who takes responsibility for the choices they make. Someone who doesn't is not an adult at any age. Aspergers victims are as disabled as a blind, mute,or any handicapped person who can, or choose not to be "handy-capable. His biological parents validate nasty behavior and there he has no guidance, no restrictions,which enables not changing, but he gets tired of their lazy, selfish, stupid lifestyle they taught him and allow him to continue in it.
He comes here, stays 4-6 days and nights a week, then goes off the edge. He displays all the flapping, clapping arms, little professor of each useless concern that completely envelops then disappears from his life, his addiction to tactile, stimulation of strings wires, mostly tape. Needs each taste smell and sight to be predictably comfortable and "never changed" can only deal with immediate, self-obsession, never finishes anything: School, relationships, license, or simple chores, and personal habits.
I need rewards and consequences that respond to his feeling of the need for immediate gratification for good choices, to re-adjust how he sees what will give him immediate positive valued results, and remind him to stay clear of consistent and just as immediate negative responses for bad choices, like pavlov's dog, he will go to the treat.

He will often opt to not eat, drink, shower, quit jobs, relationships if he doesn't see an immediate gratification regardless of his conduct. He has enough nasty friends and family associates, to get alcohol, drugs, friends, things, money, girlfriends, in trade for what he can give to offset cost of what he wants. By selling enough of the drugs to pay for what he wants, or being as nasty as homies want him to be, he can get them to hook him up, when he hasn't earned what is needed to satisfy. But quickly he longs for the consistency and safe, warm, predictable home he has here.
I need him to see good & bad consequences as the natural results of his choices, not as something I am providing or withholding. It seems the only way to make this even a little better is for him "selfishly" make better choices, if he thinks better choices will help him get what he wants, and that bad choices will not gratify him in the short-term or the long-term. I need creative rewards (( for him to feel he is rewarding himself)) and punishments ((for him to feel like his bad choices always result in him punishing himself)) do you understand that? Can you help me with that?

There is a fundamental problem in treating an adult as a child using creative reinforcement techniques when he is engaging in adult behavior of work and play. Were he socially outcast by those homies who can provide him with drugs, booze, music and sex, I would think differently. I can't believe that you won't even do the most basic adult step of charging rent, on the grounds that he will get what he wants anyway by selling drugs. I see not one bit of logic to that.

If you won't charge him to sleep under your mortgaged roof and eat your expensive food, I'd throw him out, send him to his bio dad, hard as it may feel and ruinous though it may seem. It isn't working the way you are doing it. He KNOWS how to use you. I doubt very much that he is of low intelligence.