Experience successfully growing a user base for an app;
Experience in business development and marketing, preferably of a subscription-based digital product or SaaS;
Hands-on mentality & Result-oriented;
Proficiency in English;

Since the project doesn't make profit currently it's ok if you keep your job or side hustles and join part-time as long as you can contribute a significant amount of time.
I'm also keeping my job for now but usually I'm able to spare a lot of time for this project.