Building a mobile app portfolio to $15k+/mo

Sebastian Röhl's first mobile app never got traction, but he learned from it and applied those lessons to his second app — HabitKit. Now, it's making more than $15k/mo.

Here's Sebastian on how he did it. 👇

Back and forth between employment and building

I first discovered the Indie Hackers community in 2019. I was finishing up university and I got super inspired by all the cool people sharing details about their businesses on the IH podcast.

I worked as a Software Engineer for three years, but I wanted creative freedom: being in charge of my own products, choosing my daily tasks spontaneously, and building a lifestyle where I could work on what I love. So, in 2022, I left my job to pursue my dream of becoming an indie hacker.

A year later, with limited traction, I returned to my old job and turned app development into a side hustle. But, as my apps began generating enough revenue to support my lifestyle, I left my job again in February 2024.

I'm currently working on three mobile apps available on both the App Store and Google Play:

• HabitKit: My flagship app and main revenue source. It's a minimalist habit tracking app that displays consistency in a GitHub-like grid. It hit $15k in monthly revenue in November of 2024. I'm not sharing specific numbers anymore, but it has continued to grow since then.

• Liftbear: My first app, born from my passion for weightlifting when I couldn't find a tracking app that met all my needs.

• WinDiary: My third app, created to help me remember past victories and personal achievements, especially during difficult times.

Learning from his mistakes

My first product, Liftbear, was developed over the course of six months and never gained any traction. After reflecting on what went wrong with it, I decided to pursue a completely new idea: HabitKit, a minimalist habit tracking app.

This time, I took a different approach. I set myself a tight deadline of just 2 months to release the first version, forcing me to keep the scope small and focused on the core functionality.

Throughout the entire development process, I built HabitKit in public on Twitter, sharing everything about my journey and progress. I posted screenshots from the early development stages, asked for feedback from my audience, and added their suggestions quickly.

Cross-platform development

I mostly use Flutter for my apps because it allows me to build for iOS and Android with one codebase. It’s fast to develop, and I really like the design flexibility.

On the backend side, I actually don’t have much: HabitKit is fully local and privacy-focused, so there’s no external server. I use SQLite for local data storage.

For subscriptions, I use RevenueCat, and for analytics, I use Appfigures. For ASO (App Store Optimization), I usually use Astro.

I recently started developing a new app too —  a Pomodoro focus timer. This one will be built for iOS with native technologies — SwiftUI, SwiftData, iCloud Sync, etc.

Subscriptions and lifetime deals

My business model is pretty simple: All my apps use the freemium model. You can download and use them for free, but there’s a Pro version that unlocks extra features.

For HabitKit, I offer monthly and yearly subscriptions, and also a lifetime one-time purchase. That combination works really well, because some users prefer to pay once and be done with it, while others are fine with a small monthly fee.

January is always the best month of the year, because everyone wants to build new habits. That’s where most of my revenue is made.

ASO and BIP

Most of my users come directly from the App Store and Google Play. I've spent a lot of time learning about App Store Optimization (ASO) and here's what it comes down to:

• Good screenshots

• Great title + subtitle

• The right keywords

• And a clear description

Besides that, Twitter has been my main channel. I talk about my indie hacking journey and post updates, screenshots, new features, etc.

People like to see behind the scenes, and sometimes my posts get shared and bring a lot of new downloads. This was super important at the beginning, and it still helps a lot — both with visibility and motivation.

Don't give up

One of the biggest challenges was staying patient and motivated. Mobile apps usually don’t take off right away, and for a long time, it felt like I was building into the void. There were months where nothing really moved, and it’s hard to keep going when you don’t see results — especially when your savings are draining away.

So, don’t give up too early. The first few months are usually slow, and it can feel like nobody cares. But if you keep improving, listening to users, and sharing your progress online, things can change really fast.

That said, not every app will be a success and that’s totally fine. You just have to keep learning and move on to the next one.

What's next?

Right now, my main goal is to keep improving HabitKit and make it even more useful for people who want to build better habits. There are still many ideas I want to add!

At the same time, I’m also working on a new app, a Pomodoro focus timer for iOS. It’s a small, fun project where I want to combine a clean design with simple productivity tools. I already have some early builds running, and I’m really excited about how it’s turning out.

Long-term, I just want to keep growing my small app business, stay independent, and build products that people actually enjoy using every day.

I build my apps in public on X and LinkedIn. I also write a weekly newsletter called “Building An Indie App Business” where I try to share extended insights about my life as a full-time indie hacker.

And make sure to check out my app HabitKit.