Kirby said before becoming a dad 10 months ago he enjoyed building work around his own home but advertising was the only job he knew.
With backing from his wife, Kirby took the plunge - and the pay cut.
Most building apprentices start on minimum wage, moving up the pay scale as they become more proficient.
Kirby started on slightly higher pay, reflecting the skills not related to building that he brought to the site, but it still meant budgeting to live off his apprentice's salary.
Kirby's boss at Licensed Renovations, Russell Clark, said it was an easy choice for him to take on an adult apprentice with life experience under his belt.
Although Kirby's building knowledge is light, he brings client relationship skills some younger guys don't have, making him a valuable addition to the team, said Clark.
"It's harder for him than it is for me because he has his own house, a family and a baby and the pay cut is dramatic."
It was the first time he had employed an apprentice who had come from an office job, but he had spoken to people working in engineering or mechanical trades who wanted to get outdoors.
Ruma Karaitiana, former chief executive of the BCITO, said the organisation that supports building apprenticeships, said an apprenticeship was a perfect choice for those wanting a change of career, especially with today's high demand for skilled people.
"Keeping the mind active by learning a new skill as well as getting fit by moving around a lot more during the day is a healthy change compared to a desk-bound role.
"For those who want to work outdoors in the fresh air, a building trade is also the way to go.
"It's good work for the soul - being able to stand back at the end of a job and see what you've created.
"It's very rewarding."
Kirby is now enjoying million-dollar views while working on a villa renovation in Birkenhead, but once he is qualified - he hopes within two years - he wants to build affordable homes.
He said he has everything he wants in life and now wants to give back.
As for ditching adland: "I have absolutely zero regrets."