Self-hosting requirements/scaling Is there any reason the mySQL, CraftCMS, and assets/images/content can't all live on the same server, assuming the server is appropriately sized and backed up?

Are there any sizing/scaling guidelines?
No reason at all, that should work perfectly fine.

In fact, at least 90% of my projects keep files, database, and assets all on the same server. For the remaining 10%, I'm usually only moving the assets to Amazon S3. Everything else continues to live on the same server.