Mosaico: Where can I find the source code of my mailing?
I believe you can set the "Mailing Visibility" option (accessed by clicking the "Advanced Mailing Options" button on the 3. Options page of the Mosaico workflow) to "Public Pages" which will create a public HTML page that visitors can view, accessed by a tokenized link in the email itself. You should be able to get the HTML from this page and add it to your homepage... or just add a link to that public page.


  Mailing Visibility
  
  This option controls who can view the contents of
  this email on your website. The link can be included by inserting the
  "Mailing permalink" token (place it in a link when composing in HTML
  mode).
  
  The options for mailing visibility are:
  
  "Public Pages" will make the content of this mailing viewable everyone
  who has the permission "view public CiviMail content". Note that even
  people who did not receive the mailing would be able to find it via
  search engines. "User and User Admin Only" means that only users that
  received the mailing or administrators can view this email on your
  website; users must be logged in to view the message.