What to do before leaving your job to found a startup

One more important item that isn't listed in the article:

Step 0 - Carefully read your current employment contract.

Employment contracts in the tech industry will often have provisions that cover intellectual property assignment and other activities. These clauses typically stipulate that any ideas, inventions, concepts, designs (etc.) that you create during your full-time employment with a company are the sole and exclusive property of the company (and not you, the direct inventor). Depending upon the country/state/region, you may have some rights afforded to you if you create (and document as such) any inventions outside of the workplace without using any company trade secrets or technology, so long as your invention does not relate to the current or demonstrably anticipated R&D of the company.

Many companies have these types of clauses in their employment contracts for defensive purposes to protect the company against copyright claims from its employees. As a result, not all companies will enforce (via litigation) these provisions and ultimately don't care if their employees are building and releasing side projects in their spare time. However, some companies do care, so you should be clear about your legal status before jumping to start your company.