I am a bit confused why you are starting a business, but asking how to best monetize it. That is a red flag, at the start.

In my experience, when you are starting (or looking to gain more clients), defining a niche is a far better strategy than being a generalist. That said, once you are established, you can expand your service offerings. But at the start, you must be known for something (a niche), otherwise, you’ll be known for nothing.

By choosing a niche, you can position yourself as a true expert and give your clients the assurance that you understand their needs, speak their language, and know how to solve their problems.

As a generalist, you are likely to be seen as a “Me too!” A widget who can be replaced at any time. Further, a widget often relies on competing on price, as there is no differentiator between you and the next widget. You are interchangeable. Therefore, you must be cheaper than the next widget and a race to the bottom ensues.

And be careful, because a race to the bottom is not one you want to win.

Dominate a niche, and then add another. Keep doing that until you organically become 'generalized'.

You're asking two questions. On the niche v broad question, I agree with the other posters that going niche is a good strategy. You can carve out a space more easily. That said, it may not be super easy to expand out of a nice once you plant yourself in it. You didn't specify the niche you're exploring so hard to comment beyond that.

As for monetizing, your second question, a couple of things come to mind such as services like relocation, apartment hunt, taxation and financial services. Visa services could be your lead product, with a lot of add ons one you land the customer.

I'll give you an unconventional answer. The best way to know which one is better, is to try both. Yep. No point starting niche and then going broad, or starting broad then going niche. Just invent an alter ego for both, until you realise which one is better. You will have to work twice as hard, but it will be worth it in the end.