Mr. Obvious wrote:
The one thing I would advise is make sure that you are 100% committed prior to pursuing this. I knew a couple who moved to adopt an older girl. She had a lot of behavioral problems (pretty common for somebody who is in the system) that they thought they could just "love" out of her. It didn't work and they were naive to think that, but they ended up dumping her back into the foster care system. It just screwed up the girl worse. Your kid seems like a great kid to you but it is likely that whatever has placed him in foster care comes with some unique challenges. Don't be naive about that.
Also consider how this is going to affect your own son. Adopting another child is a situation that can be good for everyone, but you're going to have to handle your son's feelings with care.
When you adopt a child, he's YOUR SON. You have to love him 100%. One of the worst things you could do is adopt him and then make him feel like an outsider, like he owes you special gratitude that your own son doesn't, and like he's not a real part of your family.
But on the other hand, your son shouldn't feel that he's being marginalized or replaced. He needs to realize that the family dynamic will change and that he'll need to make compromises. He needs to be completely committed to having a new brother too.
And despite your best efforts, no matter how fair and understanding everyone tries to be, these feelings probably will surface. The boys may fight and say damaging things, and some of those things may be things they really need to express and deal with. If you're prepared for these conflicts and everyone in your family is committed to having a new, teenaged child in the family, than it will be worthwhile, but don't take it on until you've really considered all the problems you could be dealing with.