I know I'm in England rather than the USA, but I've found a way to get round the "must be qualified" problem.
My local
college is so short of teachers in some crucial areas (including computers and information technology) that they were willing to take me on as a part-time lecturer, pay for and provide all my training to get quelified as a teacher, and allow me to do other work when I'm not actually teaching.
So I teach groups of 16-19-year-olds about computer topics for 8 hours a week, attend teaching classes for 4 hours a week, spend a lot of time travelling between home, college and customer sites, and fill the rest of my waking hours with contract software development work to feed my family. Currently the teaching provides about half the income we need to live on, but when I do get some paid software work, it quickly adds up.
My "cunning plan" is to rack up a series of teaching qualifications and a year or so of solid experience, then try and tap the lucrative corporate training market.