Realistically? Probably nothing to negative...when you take into account the hundreds of thousands of teenagers a year that use prohormones/DS (every single one of my friends that are between 18-23 that I lift with have), most of them turn out fine with little to no consequences. Everyone is different and there is more risk involved the younger you are so take that into consideration.
Also, if you do cycle, do not do a dbol only cycle. Use test and dbol at least.
That said, many many kids in college/high school use enormous amounts of recreational drugs and alcohol with no second thought. I don't think choosing to use AAS/DS over those drugs is any worse, yet using AAS at a young age is condemned by steroid communities.
The best thing to do is know the risk and make an informed decision. If arnold hadn't started at 14 or 15 then we probably would not have the icon we have today.