The main difference is that with a small business you have an established product or service and a business model that's known to be working whereas a startup i

The main difference is that with a small business you have an established product or service and a business model that's known to be working whereas a startup is all about developing a new product or service, finding product-market fit and a scalable business model that works for that. So, a startup is a series of experiments with largely unknown outcomes while a small business - though still allowing for experiments and different approaches on a smaller scale - deals with more predictable outcomes. That said, the question of "startup vs. small business" isn't a clear-cut dichotomy but often a continuum. A small business offering a service can also experiment with addressing a particular market niche, for instance. This is a common theme for small / 1-person software consulting businesses.