I'm planning on doing it on salary and savings only (13 year timeframe from now to FIRE and have house paid off). I am self-employed at the moment though, and that is helping boost my income.I think the biggest danger is assuming you can't do it. If you start now, even if you can't fully realize it - you can (at a minimum) severely scale back your work plans/schedule in later years. You could work PT at something fun, instead of having to work at your current job. If you assume it's not possible there could be a huge problem for you down the road.