This seems like a really backwards approach. If you can code, create a few good paid apps and start generating passive income. Then you'll no longer need to sell your time at all.
I think we need look no further than patio11 to see just how hard it is to make "good paid apps" for a living. We love seeing the Angry Birds runaway successes, but it can be a slog and really slow going. People just starting out can work on free apps as a learning exercise during or just after college and get picked up by a big name company doing great stuff.
Alot of mobile development companies recruit people based on existing experience making apps. Some app makers push their app development services more aggressively than their released apps (alot of them give their apps away to show off their skills to potential clients).
Perhaps the free app maker's ideas aren't polished or just not good enough to stand alone, but the functionality may wow someone looking to take on a technical co-founder or hire a lead developer to produce a bankable product.
1. Create a few good paid apps
2. ????
3. Get enough passive income that you'll no longer need to work
Contrariwise, free software has no barrier to entry at all. Just being free is a marketing campaign in itself. You're much more likely to get wide adoption with free software, so if you don't feel capable of marketing and supporting a product, it at least is good advertising for your skills.
If you want your free thing to take off, you still need to market it and do all the other things you describe. The barrier to entry is almost exactly the same, except that with a paid product you need to figure out a way to accept payments.
For a real-world example, free app downloads on the iPhone positively dominate paid apps — that's why they have separate "Top Downloaded" lists.
This is certainly one way (and a valid way), to do it. But not everyone wants to/can sell. Its a completely different skillset and not everyone is good at it.
Writing good (free) apps, is good for one's portfolio, which helps in freelancing/job market.