Building and shipping an app is always more work than you think. Coding somehow always takes me twice the time I estimated. Testing takes as much time as coding. Making the app look good requires countless iterations. Preparing the app store screenshot takes forever. You’ll need to use many tools you don’t completely know how to use.
My first app was an overly simple, minimalistic music player with just one original feature. It took me about two intense full-time weeks to get to a working prototype and four weeks to release it in the store.
TextingStory required solving a few technical challenges and it took me a couple months to ship, almost full-time. Thankfully, I was freelancing as a team-building games designer at the time and had some space in between contracts.
I had never done iOS development before doing my first app but I’ve worked with multiple experienced app developers since and I still think it would be a mistake to underestimate the amount of work needed. You don’t have to go full-time but be prepared to carve out significant timeframes.
Aim for a simple version of your app first and make sure you can devote a significant amount of time to your project to maximize the chances of reaching a store release.