I think its a great achievement in itself but your post does push people in the thinking of 'i can just make a no work sustainable something as a service app and become rich'.

I don't think it works.

I think the best bet by far is either to optimize your job salary (switching after 2-3 years, being proactive, trying leetcode, persuing FAANG) or following FIRE.

$500 would be 5h per month freelancing.

And to be really fair, he would first calculate all hours invested and he needs to calculate/estimate further time involvment.

For creating your own small company/business, thats probably a doable thing but still much more high risk than anything else.