An investor turned a century-old house into a rental that cash flows $2,500 a month. He shares how he financed it with 5% down.

The Seattle-based millennial, who supplements his engineering salary with rental income, looks for large homes — at least 3,000 square feet — with unfinished basements, which give him room to add value.

His strategy is to buy and hold long-term rentals, then rent them out by the room.

"The more rooms, the more cash flow," Keane-Rivera, who has 19 units across three properties, told Business Insider.

He opened the books on his latest acquisition: a roughly 100-year-old, 3,900-square-foot house in Kent, Washington.