My answer: Before you ask for investor money.
There are some reasons why:
It shows you're actually committed. If someone approaches me without going full-time, I ask myself "Why should I bet on this venture when the founder isn't willing to do the same?"
You can get traction prior to fundraising. If you're not working, you can go try to pre-sell some customers or run experiments in the market to validate your beliefs. Getting more traction can result in better terms from investors.
You can determine if you're actually committed. If you're not willing to dip into personal savings for six months, are you and your family really ready for start-up life?
It's a positive signal about your decision-making. At early stages, startup success is most dependent upon the execution ability of the founders. If you've lived your life such that you're able to live for a year without income, an investor will know you've got self-discipline and a willingness to sacrifice short-term pleasure for long-term success.
If you're not willing to plan for and take a little personal risk to start a business, don't ask investors to take that risk for you.