I make ~300/mo off of a peer-to-peer loan management software I created for lenders off of 0 marketing (just word of mouth sales). I have some residual revenue

I make ~300/mo off of a peer-to-peer loan management software I created for lenders off of 0 marketing (just word of mouth sales). I have some residual revenue along those same lines for a book I wrote in 2015 on helping junior developers get hired at their first job (link in bio if interested).