Possible, but time intensive
This concept is being done. I think I read in one of the national newspapers in Canada (National Post or Globe and Mail) that a couple of young guys are doing something like this already. Basically, they're leasing computers pre-installed with Windows and MS Office apps, complete with support and Internet acess for approx. $150/mo. Seems to be fairly popular to date. Although, this is for businesses, not for home users. The one interesting thing about their setup is that all of the pre-installed programs are on a partition that's read-only, and all user data is stored on a different read/write partition, thus greatly decreasing the possiblility of users screwing the systems up. And, of course, profit margins could be higher when using Linux, as you can just buy blank boxes and install whatever you want without license fees.
Not a bad concept for businesses. Might work for home users. The one problem I see is that system administration can be time intensive. Some users, especially home users, may not be willing to pay what you're worth, especially in a per hour situation. Remote admin protocols (telnet, ssh, vnc, x) would be ideal, but as the author mentioned, using them without a static IP is a pain. And, the more boxes you have to admin, the more people you're going to have to hire. I just can't see getting around that.