Sounds like what most of us want. I would like to be at the point where if my job laid me off... I can still pay my mortgage and bills and not have to worry.
I would love to develop that saas web app that many people use and it is enough for me that I could even quit my day job. And sure enough, I'm working on it too.
The solution is this: Find a common problem people have. Solve it. Charge for it. Market it. Sell it. Prosper.
If the solution already exists and someone is charging for it, than find a way to make it better (and possibly cheaper though this is not always necessary).
How I usually do this is: I have a problem. I want to solve it. If I have a problem, it is more than likely that others have the same problem too. It is almost unlikely that NO ONE but me has that same problem.
For example, I wanted a place where I could easily create a web page on the Internet, set my own URL, change the way the page looks, and share it with others. The result was a free web app I developed called MyPost ( https://mypost.io ). I shared it on here and on Twitter a few times... and now the world is using it daily. I've seen it being used in places as far as Russia and the Philippines. I had gotten the idea from another web app that .. was basically lacking a lot of what I wanted to do. So I created my own.
As far as doing your own research... sign up for a website like: http://oppsdaily.com/
Don't tackle every problem, but seek to get in touch or turn it into your own. OR just use to get ideas about problems people have.
You can also navigate to websites like ProductHunt and get ideas... sure, products already exist, but there is nothing wrong with re-creating them, making them better, etc. After all.. not everyone drives a Chevy. There is Ford, Toyota, Audi, Acura, etc. Not everyone uses T-Mobile. There is Sprint, Verizon, AT&T, etc.
It is illegal to copy a product outright where it looks EXACTLY the same. It is not illegal to make a clone of another web app. Good luck. Always be working on something.. you'll get to where you want to be eventually.