Lately I've been looking into renting out a server from SiteGround and doing some reseller hosting. However, I'm not sure exactly how to go about doing it. I have a VPS set up at the moment, but renting out a VPS large enough to do reseller hosting will be expensive -- to say the least. I know a large part of reseller hosting is streamlining WordPress sites, which in itself isn't difficult, though I've never done a project like this before. The passive income would be really nice though.
Come to think of it, there is always the option of making the server myself and hosting the websites on-site. With this, I'll be able to setup my own VPS, NAS, as well as website. So I'll also look into that. The likely solution would be to buy a used server from eBay or something, wouldn't it?