Doctors told Gordon he had a couple of years to live after the cancer spread rapidly to his pelvis and chest in just five months.
He was placed on palliative care and given hormone therapy to manage the illness.
But a trip to the United States with the school's cross-country team last month could have saved his life.
Gordon said he sought a second opinion from leading oncologists in Los Angeles who gave him hope of killing the cancer through strong radiation.
"New Zealand doctors didn't want to go down that path."
The treatment, however, will cost $38,000.
The father of two young boys, aged 13 and 8, said he would mortgage his house - but students, their parents and his employer have come to the rescue.
Auckland Grammar parent Debbie Burridge - whose son was coached by Gordon - created a donation page on website Give A Little, which has already raised $20,000.
Among the donors were current students, old boys and elite triathletes including Clarke Ellice. Marathon runner Craig Wigglesworth wrote: "Looking forward to you running past me for years to come".
Distance-squad students will wash cars, bikes, and surf boards today for their coach.
The car-wash fundraiser will start from 9.30am at Auckland Grammar School, Epsom.
Donate: givealittle.co.nz/cause/rodneygordontrust