Justin Jackson has written this wonderful article about how to choose a market for bootstrapped business
https://justinjackson.ca/niche
There is an old internet myth that any niche on the internet will grasp thousands of users.
But that's not true
Many would have heard about 1000 true fans theory by Kevin Kelly too that if you got only 1000 true fans for your product or service that is more than enough to make decent money.
But practically finding those fans are really hard.
You have to attract millions of users to get reasonable thousand customers.
When choosing a market for bootstrapped business, you have to choose a growing market that has a significant number.
This significant number matters as you need a large number of customers for your business to sustain.
Niche market doesn't mean you have to serve a small market where there is no competition. Niche market means that you got a large base of users where you can expand fast and get a significant percentage of that market.
For example, Bjorn made Shopify apps for nearly 500k Shopify customers back then and so he was able to attract a good number in a few years. As the market is huge and he was expanding, it was easy for him as well to expand and gain users.
Another example would be, when Justin Jackson (author of this article) started Transistor a podcast hosting company, the podcast industry was just expanding and a large number of people are starting a podcast. So it was easy for him to reach out to customers and build a sustainable business in a few years.
So the moral is when you are trying to find a niche market, think of it like
Hope you find this summary useful :)