To be honest all my projects created till now. They are all super low-cost per month (around 10$ per month) and eventually they will grow.

- https://caseconverter.pro/app - a simple online case converter, could probably grow it with SEO

- https://getworkrecognized.com - app to keep a work diary and create self-reviews, actually paid for itself. Got promoted twice within 2.5 years at current company

- https://linkedium.com - app to schedule LinkedIn posts, mainly for marketing use of the other projects; its also not live yet