Do not get your hopes up to high.
This is just as true for published as it is for unpublished writers. I am not saying that you send off your manuscript and immediately sink into The Pit of Bottomless Despair. What I am saying is to not assume that the manuscript is going to result in a 10 book deal.
By the same token, do not expect your publisher, regardless of the size (although I find this to be true of large more than small) to make a huge marketing push for your first (or even your third) book. They may have massive resources, but they are limited, and like everyone else, they prefer to sink them into sure things -- like Harry Potter. It is very rare for publishers to rent you a bus with your book's jacket art on it and haul you around the country. (Scholastic did it for The Land of Eloyn's author, but, again, unusual.) Instead, expect to have to send your own postcards and schedule your own book-signings.
No one said writing was glamourous -- and if they did, they are clearly living in a parallel universe.