Joshua Dorkin didn’t have to go to Trump University to learn a difficult lesson about real estate investing. In the early 2000s, Dorkin bought rental property in St. Louis and—after adding up what he could charge for rent and subtracting his expected expenses—predicted he’d make a tidy profit. He was wrong. Dorkin failed to account for costly evictions, irresponsible tenants, inattentive property managers, and unforeseen repairs, such as mending a three-foot-wide hole cut through a kitchen floor.

He tried to solve his problems by reading real estate how-to manuals, but they made no mention of the real-life issues landlords face—like what to do when someone cuts a three-foot hole in the kitchen floor. So, in 2004, Dorkin launched BiggerPockets, a website for real estate investors to ask and answer each other’s questions—like a Reddit for property owners. As the message board gained a following, Dorkin quit his teaching job, moved to Denver (for quality of life reasons), and focused on the website full time. He convinced a slew of real estate players, such as veteran house-flippers and rental-property investors, to contribute their know-how to BiggerPockets’ educational blog; added a marketplace for lenders and others to pitch their services; and installed analytic tools such as a calculator that crunches everything from local property taxes to vacancy rates to determine whether that split-level ranch will make for a profitable rental investment. The site became so successful that in 2013, BiggerPockets, which had been a one-man show, began hiring employees to support a bevy of new products.

Today, BiggerPockets boasts more than 725,000 members, produces the top-rated real estate podcast on iTunes, and last year raked in $7 million in revenue through advertising, premium memberships, and partnerships with companies like credit-rating agency TransUnion. Nearly 30 people work out of the company’s RiNo office. BiggerPockets has also added a publishing arm, which released Set For Life on April 23—just in time for the height of house-hunting season. The book teaches readers how to limit spending while increasing income by using techniques like “house hacking”: buying a multifamily property, such as a duplex, and living in one unit while renting out the other(s).

Dorkin, 41, won’t be hacking houses anytime soon. His wife and three daughters wouldn’t take too kindly to sharing their space. Plus, he doesn’t own any rental properties outright anymore, simply because BiggerPockets requires too much of his attention. But that’s OK. He’s still well on his way to becoming a mogul— just less Donald Trump and more Rupert Murdoch.