Most start-up enterprises when they are founded would be: Large-scale enterprises Medium-scale enterprises Not-for-profit enterprises Small-scale enterprises

Most start-up enterprises when they are founded would be Small-scale enterprises.

Here's why:

1. Definition: Start-ups are newly established businesses. They are usually founded by one or a few individuals who aim to develop a unique product or service and bring it to market.

2. Resources: At the beginning, start-ups usually have limited resources including capital, human resources, and operational capacities. This makes them small in scale.

3. Growth: While the goal of many start-ups is to grow and expand, this is a process that takes time. They may start small, but with the right strategies and market conditions, they can grow to become medium or large-scale enterprises.

4. Not-for-profit: This term refers to organizations that use their income to achieve their goals rather than distributing it as profit or dividends. While some start-ups may have social goals, they are typically for-profit entities. They aim to make profits and provide returns to their founders and investors.

So, based on these points, it's safe to say that most start-up enterprises when they are founded would be small-scale enterprises.