That's a difficult quesion to answer. Let me try to answer it by breaking the question down into two parts:
1) How long to make your first app that is useful and polished enough for publication, but it's free?
If you already have programming experience, like I did, the courses I linked to you have you cloning real apps on the App store that are both free and cost money within a couple hours. These are populate apps that people love. It's not hard to clone an existing app once you understand the fundamentals of programming, specifically the XCode framework and Swift's syntax.
If you don't have any programming experience then of course it would take you longer. Those same courses teach the basics of programming through Swift examples, I believe it's about 5-10 hours worth of lectures. However, they only cover the basics such as if-statements, loops, etc. This would be enough knowledge for your to start cloning the games in the lectures while still understanding the code.
2) How long to make an app that sells for money in the App store?
This is much more difficult. You are no longer cloning existing apps from a course where the app design, assets, and code are provided for you. And this highly depends on the complexity of the app and your experience as a programmer. The courses are just the beginning. If the app is simple, then all that's holding you back is your imagination. If the app is complex, such as a mid-sized game, then you would need understanding of programming design principles, algorithms, AI, pathfinding, data structures, asset creation (if you're not hiring someone), etc.
That's just the technical know-how. If you want to make money, you need understanding of marketing, monetization, branding, support mediums, etc. Even if you make a very good app, how are you going to tell people about it?
You asked about me, so here is my story. After I graduated with my bachelor's in Computer Science I wanted to make games (what a surprise, right?). I read Apple's documentation for their game libraries. I took some Udemy courses on both app and game development and cloned a dozen apps/games, which took me about six months. I started to feel very confident as an iOS developer and applied for a full-time job. I got the job and quickly learned that I didn't know ****. So I kept learning and growing. One year later, which takes us to present time, I feel comfortable at my job and can meet our client's needs. I have every intention of having my own software company in the future and am working towards that. Right now I'm reading about game theory and design principles. Because I have a full-time job and a family, this will take me much longer, but I love doing it and if you love what you do you don't work a day in your life.
My advice to you is this. If you love software development, just start growing your skills and developing as a person without concern of the money. Pick a niche, something to specialize in. Obviously we are talking iOS development here, but for me specifically, game development in iOS.
Become a master Google searcher. I can't stress this enough. There is simply too much to learn and research. Hone your skills to search for exactly what your looking for. Learn the search engine's filters, such as intitle, exclusions ( - ), etc. If you have a problem, especially as a beginner, I promise you that many more have already asked it and it has been answered. It will save you a lot more time than posting on the forums and waiting for a response.
Learn to read Apple's documentation. Read books about programming. Read lots of codes from other programmers to see how their mind clicks. Maybe you'll learn a gem or two.
Yes, you can make a living as an iOS developer. It's different for every person. You have to figure out what works for you 😉
