This would only require the investment of your time. Start with a blog on something you love. It could be anything. From a travel blog containing pictures of your travels to a sports blog dedicated to your favorite team/sport. You can blog about anything and everything. It doesn't matter. But write regularly! I've read that an online magazine editor would personally prefer someone who posts something daily over someone who writes long posts once or twice a week.
In 2017, I ended up deploying roughly $611,000 into stocks and $604,327 into municipal bonds. The stock allocation should boost dividend income by about $12,500 a year, and the municipal-bond portion should boost income by about $18,000 a year after tax ($26,000 pre-tax). Therefore, total passive income gets an about $38,500 lift, which recovers over half of my $60,000 loss from selling the house.

Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.