My husband and I want to add a second story on our current home as well as push out our backyard to our property line (which is on an alley). The latter is something all of our neighbors on the alley have done and it will require a retaining wall. The problem is that we don't know where to start. I want to contact someone to evaluate what structural requirements there are to add the second story and get a budget estimate for the project(s). I just don't know who that "someone" is and what to expect.

Do I contact a contractor? an architect? design/build? structural engineer? landscape architect (for the retaining wall/yard project)? Do I need to select the professional with whom I intend to complete the job? What would be a reasonable fee for this? (We are in Los Angeles.) I've read the articles here on getting started, but I feel like we are at an earlier step (an information gathering step to determine whether we are going to embark on the project).

Thanks in advance for any information or direction you can provide.