Welcome. Good thinking comming here to find answers. Great wording you question too. No flames here.
First off, we all hope everything is okay with you, your family, and your house. If not, our hearts go out to you.
Second, Bushmaster, or RRA, are excellent choices. If your wanting a carbine, since your from an area with high humidity, I suggest a chrome lined barrel. Asking a gun dealer this simple question will make you look like your somewhat compitent. Ask him to show you that it's chrome lined. when he pulls back the charging handle, take a look inside the chamber. if it is a light grey, or silver color it's chrome lined. if it's black, it isn't. look for a bayonet lug, and A2 flash hider. This will tell you if the weapon is a newer produciton weapon, or something he is just trying to get rid of that he had in stock before the ban expired. Also check to see that the stock actually collapses, and is not pinned into the open position. Your also looking to make sure the carry handle comes off. that's a no brainer though, you'll be able to tell that at frist glance. If your not sure on what these terms are, someone here can post pics of what you need to look for. That will make it easier for you.
Hope this helps!