This app replaced my 9-5 ($150K/year)

Executive overview

Most side projects fail because founders overcomplicate them or wait until they can go full-time. Christian Konnerth built a simple wishlist app over six years — first as a student, then alongside a full-time job — and grew it to $150K/year before quitting.

Start with a real problem you have. Set micro-goals instead of revenue targets. Build for users first; growth and monetisation follow.

The unlock: treating users like individuals — personal follow-up emails after fixing their issues — turned happy users into a steady stream of App Store reviews.

Managing a side project alongside full-time work

• Work in two daily blocks: one hour before work (support emails, analytics) and two to three hours in the evening
• Winter months are the most productive — exploit them
• Negotiate a four-day week once the project gains traction
• Working holidays combine socialising and deep work
• Surround yourself with other motivated people to protect mental health
• Be upfront with your employer — a side project makes you better at your job

Finding the right idea

• Start with a problem you or someone close to you actually has
• Build a nicer or simpler version of an existing tool if that's all the gap requires
• Avoid copying the most saturated categories (e.g. to-do lists); find the adjacent niche
• Set the smallest meaningful goal first: one stranger downloading the app, not a revenue number
• Monetisation can wait — you have a salary; use the runway

Growth without a marketing budget

• Ask friends and family for App Store reviews first — awkward but effective
• Trigger in-app review prompts only after a user completes a positive action (adding or fulfilling a wish)
• Build a personal support system from day one: save every email and feature request
• When a bug is fixed or a requested feature ships, email the specific user who raised it
• Ask a direct question in support replies to get a response; only request a review after a positive reply

Business model and numbers

• Revenue model: premium in-app purchases (custom wishlist images, membership) plus affiliate links auto-inserted when users import Amazon products
• ~99% margin — only meaningful cost is server infrastructure
• Current low-season monthly revenue: ~$6K; scales ~5x in the Christmas high season
• 1.1 million registered users; 110K monthly active users; ~4K paying customers
• Tech stack: Flutter (cross-platform), Cursor IDE, Firebase (backend, auth, analytics), RevenueCat, Superdesk

Timeline: six years from idea to full-time

• 2019 — started building as a university project
• 2020 — shipped first public version
• 2021 — landed a job as an app developer, partly on the strength of Wishlist; began full rewrite
• October 2023 — launched Wishlist 2.0; hit 100K registered users
• 2024 — ran both the full-time job and the growing app in parallel
• July 2025 — quit the job; full-time on Wishlist