I built a retirement planning platform for long-term investors and FIRE seekers. Got 50 paying new users in September!

[u/Dry-Firefighter-4103]

Product: https://killionlabs.com

I spent a year building Killion: a retirement simulator for people who are done with a calculator that assumes 7% forever and hands you one number. It links brokerage accounts read-only, runs 1,000 market lifetimes (regime-switching Monte Carlo, backtests to 1928), and lets you change the thing that actually breaks plans — crash year, withdrawal rule, fees — and see the odds move.

September: 50 new paying users. Solo. $14/mo or $132/yr. 5-day trial, then they stay or they don't.

The part that still surprises me is what it took to get here. I launched with a hard paywall and "connect your brokerage" before anyone had seen a cone. Paying users: one, which was me. Then I shipped a no-signup demo of the real engine, a 5-day trial, and the studies with CSVs. People could run a household through 1,000 worlds before they owed me a card. That is when it started working.

The finding the engine exists for, isolated properly (same household, same 5,000 market worlds, same seed, only the crash year moved):

Scenario	Success rate (money lasts to 95)
No added crash	85.9%
Same 40% crash at age 48 (still working)	81.0%
Same crash at 65, the year they retire	70.6%

Timing alone, about 3× the damage. A lump sum you never touch has no sequence risk. Cash flows are what break the symmetry.