So proud to be included in this. A lot of solopreneurs started with WordPress and moved to SaaS. I went the other way and still see so much opportunity in WordPress plugins, plugins-as-apps, and SaaS.
I presented on this a couple years ago at a WordCamp, and am giving the updated version in a week at WordCamp Belfast. https://wordpress.tv/2017/06/05/corey-maass-rapid-web-app-de...
There are also some excellent plugin markets for most eCommerce platforms if you've got the drive to develop in them. Companies using an eComm platform are likely to be actual businesses so they are willing to spend more money for a quality plugin.
The other option is building a SaaS app and using a single WordPress install or WordPress multisite as the platform. I thought this was a crazy idea a couple years ago. Now I know of dozens of apps that have WordPress as the back-end, and it works well.