I like this idea, selling wordpress is really profitable, if you take a look at themeforest.com, you will see a lot of devs making money selling their own digital products online and the beauty of this kind of business is, you can collaborate with others, like UI designers can collaborate with a developer to design a theme and also it is a one time off kind of thing, which means the moment sales started kicking in, you will earn passively.
I have heard a lot of developers encouraging others to get into it, the wordpress ecosystem is very huge, there is always something to do to earn money, from setting up websites to designing themes from scratch and building plugins also.
currently there's also building wordpress site with rest API, it is just so exciting, I will strongly advise devs to look into selling wordpres products it really looks promising.