An ideal way to solve a problem is learning all the conventional methods then find a solution that works best for you. I found that the most helpful way to figure out how much you need to retire is to first calculate your monthly expense.
Make sure you add in annual expenses such as property taxes, capital costs, and holiday spending. Also add the costs of hobbies, travel, health insurance, and long term care.
On the other hand, without a job you will not be able to contribute to 401(k) or Roth IRA since the contributions are based on earned income.