It is possible, I have a couple of really niched down directory sites (that everyone says not works, works perfectly fine) in my language that ranks position 5-6 in Google with just 7-8 articles and 5-6 free links on them that brings in around $600 each every year per site, that I made some years ago for testing. Build a bunch of those types of sites and you could get a decent side income. I really don`t do anything on them nowadays other then updating the theme and plugins, and send an invoice once per year. Total time maybe 1-2 hours per year. If I would start marketing them to businesses in the niches, I would make a lot more, I know, I´m stupid lazy.