Go for niche, but be open to pivoting and appealing to a broader audience.

Ideally, when planning your product roadmap you should build it around the needs of a specific group of users.

But there comes a time when you have conquered the TAM (unless it's a blue ocean market like health, fashion, fitness etc) and you would want to branch out into adjacent or adjoining markets.

But if you have built too deep, it might be extremely hard for you to expand and grow.

So, go vertical right now, but also account for horizontal expansion.

A few more things to account for when determining your target market:

- the interest in the type of product over time. (you don't want to build around a fad).
- whether you are solving for a bleeding neck or for a sprain. If you have demonstrated expertise, people will line up for the former.
- whether you are solving for convenience or cost. Some markets care about convenience, and others are cost-sensitive.

Get any of these wrong (these are just few of the many factors) and your product will not appeal to your target market at all.