[WalterBright]

> at what point does something go from “side project” to “business”?

When you get serious about making a substantial profit.

> And how do you tell if it’s worth trying to scale vs just leaving as is?

If you can make more money flipping burgers at McDonald's than the business, I'd try something else.

[coldtea]

>If you can make more money flipping burgers at McDonald's than the business, I'd try something else

If you can make the same or slightly less money way more leisurly and with way less demands on you than working a McDonalds, it's still a fine lifestyle for many.