I created a solution a while ago that contains a Web API 2 project (provides JSON data to mobile devices) and a Class Library (includes my data access services).
The Web
What I like to do, is to have the MVC and WebAPI project in two separate projects (separation of concerns) but let them share the same business logic.
I like to utilize the Command and Query pattern. So all commands and queries is located in another solution project, which both the MVC and WebAPI project has access to.
I deploy the MVC project on the www.domain.com
path, the WebAPI project on the api.domain.com
and enable CORS on WebAPI for the www
origin.