I've now been working with small business owners in Australia for over 15 years on their marketing implementation, but I've also had the benefit of a gifted mentor who works with business simulations and we have consulted on a number of projects together.

Within the context of starting a business there are a whole lot of variables at work, while I take a simple approach, there is an appreciation of the complexity involved.

To start you need a product, you'll need to be able to sell it, then deliver it to get paid. Then to be able to collect that money and to do that profitably ie. get paid more than it cost you to make or buy.

Obviously this is what I mean by simple, but you know there's way more than that involved:
How big do you want to get - just yourself to make a living, or to scale up?

The product for a start, this could be a service or a physical product - does it solve a problem and will someone be willing to pay you for it.
Is it a commodity product/service, or unique?
How much can you sell it for, and how much do you need to sell to make a decent living?

Commodities have to be sold in volumes to make decent revenue, whereas a unique product or service attracts a premium.

These are just some of the ideas to consider. As I mentioned, complexity is part and parcel, but needs to be navigated.

I've compiled a few videos on YouTube that you might find helpful, I will add some on business models at a future date:
https://www.youtube.com/wisepreneursaustralia
Also a very good read: https://hbr.org/1994/03/how-entrepreneurs-craft-strategies-that-work
Plus the book Where Good Ideas Come From by Steven Johnson
I hope this helps add a bit more clarity to the question you have.
https://clarity.fm/nigelrawlins