Not every idea is profitable and that is okay.
As an entrepreneur, you will get approached time and time again from people with ideas: some of them good, some of them bad. We also come up with a million ideas a day, but what you really need to do is stop and determine if the idea has value to others.
First you need to identify a problem that your idea will solve. Then you need to identify the audience that has that problem, this is your market. Once you have a well defined solution to a problem and a well defined audience, you need to determine if this is a big enough problem for your audience that they would pay money to solve it.
You will need to do a lot of market research to answer these questions and the best place to start is by simply calling people that you think would be interested. Ask them if they have the problem you are trying to solve. Ask them if they would like a solution. Ask them what features would be beneficial to them. Ask them how much they would be willing to pay for it. Now you are letting your market determine the features and cost of whatever you are offering.
By doing this market research, you are also seeing if an idea is worth pursuing. While something may be a great idea to you, the only way it is a great idea in business is if it offers value to others.