It seems the hardest problem is (always) finding the first million with which one can invest.
Some of the most popular, profitable YC startups (even just regular 'ol startups) were started on a fraction of $600k.
I encourage you to think in terms of percents. The Trinity Study says you'll need about 25x your expenses saved. If you can lower your expenses by 5k/year, you can not only invest that money, but your target also lowered by 125k. That double whammy allows diligent savers to do very well and retire on a much shorter timeline than those spending 95%+ of their paycheck.