Lighting is most definitely not your biggest issue. Lighting *is* an issue for you, but you need to take 5 steps back from worrying about lighting and focus on honing the basic technical skills every photographer must possess: Composition – Learn about it, don’t just go out and try to be ‘creative’ and call that practicing composition. There are TONS of books and videos about proper composition theory and techniques. There really are ‘rules’ about composition. Do you know any of them? Focus – Nailing focus will help provide sharp results (not withstanding any blur caused by camera shake). Metering – Learn properly how all of your different metering modes work and when you should be using them, and learn what your cameras tendencies are when metering in each of those modes so that you may input the proper EV adjustment.
You need to know your equipment backwards and forwards and strive for creating an accurate rendition of what your eye sees if you want the best basis from which to ‘enhance’ your photos with later on.
As others have said, you’re getting waaaay ahead of yourself and are trying to skip the learning process that every responsible photographer knows they need to go through. Its not as much fun as going out right away and trying to make great photos…but you simply won’t make great photos without learning the basics forwards and backwards. In other words, buying a guitar and learning a simple rock chord progression doesn’t make you a guitar player, let alone a composer/singer/songwriter. And its disingenuous to let people think that of you.
Once you have all of those basics mastered, you can then worry about learning lighting (ambient and controlled). And once you have a solid foundational knowledge on how to use light, will you then be capable of producing quality portraits….BECAUSE you took the time to learn the basics first.
Because of all this, you have absolutely no business charging people for your service. Learn the skills, then get the job.