When drawn, he confirmed taxpayer money would contribute towards paying the bill.
But Mr Hollister-Jones refused to say who the investigator is or how much his bill was potentially going to cost.
"This is a private matter between the board and the investigator," he said.
Mr Hollister-Jones said at this stage the terms of reference for the inquiry were yet to be drafted as the board was still seeking legal advice, but he hoped the terms would be finalised by the end of the week or possibly early next week.
In terms of the investigation, it was being led by the board with the assistance of the investigator, and Mr Hollister-Jones had no idea how long it would take until the terms of reference were finalised.
"But what I can say is the investigation is likely to take weeks rather than days because of what is involved and there will obviously be a number of people he will need to speak to," Mr Hollister-Jones said.
No decision has yet been made whether the investigator would travel to Kenya as part of the inquiry, and he confirmed he had not seen any Kenyan police crash report nor did he know whether there was one.
"There was a lot of confusion about the sequences of events before and after the crash, and who said what, and the aim of the inquiry was to clarify all those matters," he said.
He did not know whether Mr Fellows could be extradited to Kenya to face charges but obviously that was a matter of concern.
Kenyan man Christopher Mmata was originally thought to have been behind the wheel at the time of the crash.
Mr Mmata died in the crash, along with former Bethlehem College student Caitlin Dickson, 19, and Tauranga couple Brian and Grace Johnston, who are survived by their 10 children. The college revealed on Monday that Mr Mmata had swapped places with Mr Fellows before the crash.
