We've all thought about designing our own frame. I thought about it for awhile before I finally took the plunge to design, build, test, re-design, retest, redesign, retest (you get the idea) my own frames. Hopefully, eventually, you may get to a design you're happy with that you can possibly even market and sell to other quad enthusiasts. From my experience, I can tell you it's NOT easy! For those who are either interested in designing for the hobby, or just for yourself, here is a little advice from someone who has gone down this rabbit hole.
FLY, FLY, FLY.
I have had years of experience flying RC planes, helicopters, gliders, etc. Yet, when I started flying quads I found it to be an entirely different beast. Your best bet is to fly first, design later. Trust me, your money will be much better spent getting used to flying and learning about current frame designs and pitfalls without having to wonder if your own frame is matching up or not. You'll get a better feeling about what the needs actually are as opposed to perceived, and it will help mature your own mindset in your approach. Get involved with people who are already flying / racing and talk to them. Learn from them. They will be a great source of information and input later on. But it will help to have a reputation as a flyer as opposed to just someone throwing something in the air.
ONE AT A TIME!So, you've spent a few months learning to fly, understanding the actual needs, and in that time you learned how to use the machines and tools you will need to produce your first prototype. Now you're geared up with a great design and ready to start cutting frames to sell!! WHOA!!! Slow down. This is a great time to put the breaks on and produce one model. Understand, you WILL break it and it WILL not be all that you think it is. This is a normal part of the process. However, you will save yourself a lot of time and money if you focus on making one iteration to test, crash, redesign, build, crash, and so on until you find that about 10+ iterations later you actually have something that could potentially be a great design.
BE HONEST WITH YOURSELF
It's so exciting when you put something of your own into the air for the first time. You get pumped and ready to just go out and sell! But, take a little time to reflect on what you think your design does, and look for empirical data to support your thoughts. If you think you have the lightest frame, find out what the current light-weight competitor is. If you think it's stronger than others, do stress tests on those components. Test crash, have other people fly your frame (or use your parts) and get feedback from them. Does it really do what you think it does and perform the way it's supposed to? If not, you might have to either go back to the drawing board, or start on a different project. It's tough, and can be disheartening at times, but be willing to let it go before you spend tons of time and money on something that just doesn't work the way you think it will.
LEARN AND APPLY
So, after you've gone through many iterations of your design in 3D modeling and actual builds, you will finally arrive at something you like and are ready to put on the market. Realize that despite your best efforts to design "the best" product, you'll learn that the market may or may not be open to it. You will also find that there are always tweaks to be made on your design. Invariably you'll be going back and making a V2, V3 and so on for your designs. You may also find that the market may not necessarily be open to your design when you are ready to release. That doesn't mean that the design is bad or somehow lacking; it could just be timing and marketing. Learn from each project and move on to the next until you finally make something that people like and want. This is much of where cost comes into play. It's really advantageous being able to iterate and do small test batches when you start. Testing the waters helps you to not sweat it if / when it doesn't pan out, because you haven't lost a massive investment (except some time and small costs). Keep your production batches small for your tests. Being able to cut your own parts will save you THOUSANDS of dollars in cutting and producing. Plus, not having a ton of product on your shelves that doesn't move can help you stay motivated and not overwhelmed with non-successes.
No matter where you're at, it's true that China can make things in volume* (minimum order quantities can kill projects really quick) that can reduce your production costs. But, do consider handing over your designs to companies that may or may not reproduce your designs and sell them on the market taking away money from you. Do your research and talk to as many people as possible that have gone down this road to learn how to protect yourself as much as possible.
ABOVE ALL, HAVE FUN!!
Look, everyone wants to make money and be part of this great community! But, if you're not having fun, what's the point? You'll never get rich as one of hundreds of frame makers and producers. There will always be someone who comes up with a better design, cheaper product, and or something else that the market wants. If you put too much of your hope into this you'll probably be disappointed, so why not going in with the idea of having fun from the start?! As long as you're having fun, you'll be more motivated, more in-tune with your own ideas and flow. You will make better products and above all, you'll be having a blast doing it as opposed to trudging through each step of development. This hobby is WAY too much fun to have bad feelings associated with it. Go out and have a blast!