Good topic. I've included the house piece because you asked about NW, not just RE savings.
I've only kept good records since my late 30's, so there's some guesswork here:
Age 23, graduated from college, got a career-track job. My NW was $2000, the value of my well-used car. (The folks and part-time work paid for school, so no debt).
Age 24, got married. Our NW was $8000, the value of two worn-out cars, some wedding gifts and a couple of paychecks worth of savings.
Age 26, ready to buy a house - NW = $15,000 after some LBYM savings for a house down payment while making car payments, buying furniture, etc.
Age 26, bought the first house - NW = minus 85,000. It was scary to sign a 30-year note, but thanks to the mid-80's S&L / real estate troubles in Texas, it was a good bet and within our means. This was also about the time I began putting $100 a paycheck into a 401k. We also made several April tax-time IRA max contributions while we were still DINKs.
From there, I'm guessing we went positive around age 30. The real estate values went up quickly and we continued socking away $5000+ per year in IRA/401k's. Also, DW had a pension plan at her Megacorp job, which became a rollover IRA when she left at 30 for stay-at-home mom duty.
Mr. Lynch over at Magellan was kind to us, and real estate in our neighborhood went up some more, so I'm guessing we were on track to hit $100k around age 33.
So the key factors of hitting $100k were equal measures of house appreciation, steady (but modest) IRA & 401k contributions beginning ten years earlier, and compounding.
What actually put us over top a little earlier, though, was a windfall. Ours happened to be a legal settlement, but for others might be an inheritance. Had one of those, too, around age 40, which bumped us over the $250k milestone.
The most important factors since? More compounding, continued steady (but modest) RE fund contributions and holding onto those two windfalls in a buy-and-hold stock mutual fund portfolio.