He can score anything from just probation up to 5 years prison. Since he has addiction issues, I'm sure a judge would like to see him get treatment. The earlier he gets into treatment, the more likely he could avoid jail. Hire an attorney to help him out before this gets worse.
The Statute that you quoted is for Possession with intent as a 3rd degree felony. If this is his first adult offense he will score non-state prison up to 5 years state prison. Because he is being charged as a seller, he will most likely not be afforded a drug rehab program/diversion. However, there are still other programs in place to assist him.
This response does not create an attorney client relationship and is offered for informational purposes only. Only a lawyer fully versed on the facts and circumstances of your case can properly advise you on the case. I am licensed to practice in Florida and New York, not every state. You should always consult with an attorney licensed in your area on how best to proceed.
I see that you posed this question from Fort Lauderdale, Florida, which as you know, is situated in Broward County, Florida. In other words, it is about as different in every aspect of the courtroom management of criminal allegations asserted by the 17th Judicial Circuit's Office of the State's Attorney, when juxtaposed with the jurisdictions to the North and the South, Palm Beach County and Miami-Dade County, as one could possibly imagine. It takes a long time practicing in Broward to find mechanisms of persuasion that will actually result in a better offer from the ASA assigned to the case, and even from the trial Court. There are still some great judges left in Broward County but by and large I tell everyone, including my friends and colleagues, if you believe that there is even a minute chance that you could make a mistake, don't cross the county line into Broward. Stay in Miami-Dade or Palm Beach Counties. The difference will be mind-boggling.
Nonetheless, don't give up yet, I was just successful very recently in securing Youthful Offender sentencing for a young client of mine (he is twenty  years of age at the present time). Concededly, we are in front of one of the best judges on the Broward criminal bench in this case, but it is still something that my colleagues and I count as a major victory (sentencing for a client as a Youthful Offender, that is), as it can be secured so seldom for your clients relative the numbers in Miami-Dade and Palm Beach Counties, irrespective of the fact that the legislature clearly intended that it be used as an alternative form of sentencing for young persons who can be demonstrated to be remediable. Only those convicted of capital or life felonies fail to qualify, assuming the other basic qualifiers are met. In other words, don't focus on what he is facing; focus on what you, your son (you don't say so, but I take it that we are talking about your son in this instance); and the attorney who you decide is best suited for his case should be focusing on - convincing the Assistant State Attorney and the Court that a statute which was placed on the books for a very clearly enunciated reason should be used in that spirit whenever it is possible and there appears a likelihood that the young man or woman will benefit from the program. In my client's case we were actually able to secure a sentence of probation as a Youthful Offender, but he had followed every word of advice which I have given to him when we first met on the night he was arrested, through the plea to the Court. Aside from probation, there are obviously a wide variety of sentencing alternatives available for the Court's consideration, and that alternative which is likely to yield the best possible outcome for any given young adult is the one which the Court is most likely to choose. However, if, as was my client's case, you demonstrate to the Court that you are pursuing a course which involves a change in lifestyle, manner, actions, and even your mental approach to situations - in other words if you demonstrate to the Court that you are already effectuating positive changes in your life, and that these changes are likely to be long-term habits not short term solutions to a sentencing "problem", and nothing more than a means to avoid jail or prison, things can really turn around.
I think that most, if not all of my colleagues agree with the notion that we have to devote every possible resource, including our own, to our young clients. The most demoralizing thing that one can see is a face which becomes increasing familiar over the years, because the man or woman who at one time was a client you were able to present to the Court as first-time offender, and a young one at that, but who somehow gets lost in the system as so many young people do and eventually become repeat offenders who spend more of their lives in jail or prison than out, even if their individual sentences are each rather short, taken individually
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