One single idea which meets the needs of a narrow niche audience is not going to be enough to provide you with long term financial security. You will need to tap into a niche with many product possibilities. At a minimum enough possibilities to make it worthwhile to develop multiple products.
Say you have decided to create a eBook planning guide for weddings as your first info product for sale. A beginner in the information product business might want to start by creating a detailed product that covers all the details A to Z.
Take a look at from the viewpoint of an experienced market. It takes a lot of effort and time and money to build traffic to a website where a 2% conversion rate is good for an information product. Does it make sense to waste that effort for one $47 sale with no follow up instead of creating a lifetime stream of profit from that customer?
How best to do this? Information products are designed to serve specific needs of your target audience. A bride and groom have many separate issues to consider. You can produce dozens of guides that focus on those needs.
Sometimes, a single comprehensive information product is the way to go. But you also want to cater to the needs of your niche who don't need all of the other stuff, just what they, in particular, are seeking - like information on wedding cake flavors or homemade wedding favors for brides on a budget.
Once you deliver one outstanding information product to your customers, you'll have them on your list where you can then market your backend (follow up) products to them. This is where the true money in Internet marketing lies because you don't have to spend money to attract that customer - they're already in your database.
So make sure that you have fully explored the future product potential of your niche before you dive into product development. Check to be certain the niche provides the opportunity for branching out into a new line of products offering solutions to your customers' other problems.