The family will also take equity ownership in the business.
The Richardson family has a variety of international business interests, predominantly in real estate and also in private equity.
CEO and co-founder Ashley Ilsen said the move put the firm in a strong and highly-liquid balance sheet position.
“Ultimately a short-term lender is only as good as the funding behind them so we are delighted to partner with the Richardson family,” Ilsen said.
“The initial uptake of our development finance offering has exceeded all expectations and, despite some of the negativity in the current property market, we are all looking forward to a very successful future.”
Magnet Capital managing director and co-founder Sam Howard (pictured) added: “It is a tremendous privilege to be partnering with the Richardson family and to harness their deep real estate and wider business expertise.
“Over the past two years we have built a strong relationship with the Richardson team so we are excited to partner with them to launch Magnet Capital and provide SME builders and developers the finance they so desperately need.”