Ever heard of Rovio Entertainment? Well, most people hadn't until the company released their 52nd game. The first 51 weren't really all that great, but number 52, Angry Birds, put them on the map and netted them 200 million dollars in 2012.
The point is that not every project you do will be a success, and that's okay because finding a winning idea takes time and many attempts. Therefore, if you're working on iOS apps, and that app isn't bringing in success, try working on another one.
When I first graduated college, I worked on a few different Firefox Extensions back when writing Firefox Extensions was still cool, and I wrote about my experiences writing them on my blog. Not many people really ended up using them, as they weren't real winners, but it did evoke some interest from a lady in New York who wanted to hire someone to write a Firefox Extension that did something very similar to what one of my extensions was doing. The difference was that she had the creative ideas and energy needed to start a business, and she had the capital to pay me to invest more of my own time and energy into helping further her business goals.
Therefore, I'd suggest you continue down the path of writing your apps, but instead of just publishing them, get the word out on your blogs and social networks that you have these skills. There will be someone out there looking for someone with specialized experience, and that could very well be you. As for how much time to invest, that depends. Marketing yourself definitely takes time and dedication, and it's up to you to determine how much time you can afford to take away from other activities in order to invest that time in your projects.
As an aside, I'd suggest not focusing on your age. Ageism works both ways, and you could inadvertently talk yourself out of a nice contract wage by showing your cards. If and when someone does contact you for work, be as professional as you can, focus on what you can do well for that person, and keep in mind that you likely have knowledge and experience with something that many others either don't have or haven't demonstrated.