Sorry to revive an old thread, but I’ve been researching this topic lately and wanted to chime in with my own 2c. I really think that hosting websites for clients and having ongoing support agreements with them can be one of the easiest ways for web developers to earn somewhat ‘passive’ income.
Let’s say you charge a client $100 a month for hosting and on-call. Sometimes you’ll need to do an hour or two of work, but some months you may not have to do any work at all. That $100 is completely passive. I recently heard a web developer on the Treehouse forums say that he actively encourages all his clients to host with him and this revenue stream has grown to 40k a year for his business, and a lot of that is ‘passive’. It also helps him weather the storm when fewer clients are coming through.
Just my 2 cents. The trickiest part of this is managing recurring billing and invoicing for your ongoing hosting and support agreements. Full disclosure: I’m working on Biru, a tool to make this easier.