[Digory]

You're on the right track. A couple of rules of thumb:

1. An LLC's liability protection kicks in when you start to deal with others.

2. For the first LLC especially, you should measure the value of what's at risk, not the 'profit' or value of the business.

In (the many) states where LLCs are cheap, it makes sense to put side projects into a container sooner, not later, especially if you have significant personal assets. Your personal assets are probably worth a few hundred bucks to protect, even if you don't have outside investment.

It's a more difficult question to decide when to split out a particular side project into its own LLC.