So I can invest money and I can buy domain, I already own hosting so all I need right now is an idea, what should I open? What does not exist?
I don't think you're going to get any answers to questions like this. If someone knew of an idea which doesn't exist, they would open it themselves.
There is nothing in the world which is not exist over the internet. It is depends your own capability shows how to make money by the presence of the internet marketing.
I have a great idea as I know of something that doesn't exist. You could create a web site which gives out unique non existant ideas for free. You'd rock as you would be the only one to set it up.
You should create something you are passionate about, so you will have fun while working on it for free ... yes for free because at least few months will pass until you will see return on your investment.
If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas. Mind to share your idea first?
I always have plenty of ideas floating around in my mind but most of the times they are so grand that I started having a lack of resources to execute them .. You just need to brainstorm a little bit and pick the best one that passes through...
Your greatest success will come from within, your passion, what moves you, motivates you to get involved in something. It doesn't matter if your idea or passion exists already, what doesn't exist is your own interpretation of your passion. It is just like stories...there are only so many plots...what makes a new story, a fresh and original story, is how you view that plot/story. Same on the internet. No two people can enter the same market the same way, unless you are both using the same exact content/pov. So find something you are passionate about, and tell the world your view on that passion.
Find something you enjoy because you'll be working on it all the time I wouldn't say all ideas are used up -- you just need to find what you're interested in, do your research into the competition as you'll start to notice certain services/products that they don't offer.