"It's partly for money [$50 to $150 a day] and partly for promotion. We get a lot of people coming to our shows above ground just by playing down there, handing our cards and giving out our email."
They had also sold thousands of their CDs underground, as well as online and in Rough Trade record stores. It has been variously described as folk indie, pastoral-astral and experimental.
Saffery says that when he first went busking, the underground was a great place to strengthen his voice, develop his guitar work , find out what worked and it provided a partner for a duo.
He met fellow busker Erik Meier from New Jersey.
"We were competing for the same spots and really liked what he was doing and he really liked what I was doing so we teamed up."
They worked as a duo and shared hard times together one winter in a furniture-less flat and he says they were sometimes compared to Flight of Conchords - without the humour.
They have now added Clinton Van Gemert on upright bass, a print-maker who hails from Pittsburgh.
Meier chose the name of the band, taken from the song Little Bird Courage by a Brooklyn band he liked, Old Canes .
Their debut album, titled Maia Manu, meant Bird Courage in Maori.
The band uses xylophone, percussion, ukulele, upright bass, two acoustic guitars and melodica.
From Havelock North and Wellington, Saffery, aged 34, played trumpet as a youngster, sang in the New Zealand secondary students' choir and played acoustic guitar.
The fact his mother is American makes it easy for him to work.
He finished a law degree but his first love has been music.
Saffery lives with his lawyer girlfriend in Williamsburg, a gentrified part of Brooklyn, and he says there is a community of New Zealand musicians in the area including the Gibson family's Streets of Laredo, Liam Finn, Connan Mockasin, as well as Lorde's manager.
During the overseas tour, Bird Courage will play at the End of the Road Festival in Britain.
Saffery says he is excited to be playing there along with other Kiwi acts including Mockasin, Tiny Ruins, and Unknown Mortal Orchestra.
Saffery has gone back to waiting tables a few days a week to help with the tour costs.
But he is foremost a musician whose aim is to feel fulfilled through his song-writing and to touch people.
And now, he says, he is "living the dream".
"Now all that hard work, we are starting to get some reward for it."
