Mr Haselsteiner is a co-founder of Interhyp, Germany's largest independent mortgage distributor according to its website.
He worked for Salomon Brothers and Goldman Sachs where he met Marcus Wolsdorf, with whom in 1999 he started Interhyp, an internet-based mortgage distributor that went public in 2005.
Interhyp was taken over by ING Direct in 2008, valuing the company at more than 400 million ($633 million).
In 2011 they founded investment firm HW Capital, which specialised in investments in financial services businesses.
Mr Haselsteiner declined to comment on the purchase "as this is a pending matter in front of the Overseas Investment Office".
Valuer Mark Morice said the property appeared to attract a "considerable premium" over and above its economic value as a farm because of its proximity to Havelock North and its scenic qualities.
Sales of overseas land became an election issue following the sale of Lochinver Station near Taupo to a Chinese company.
The sale of the 13,800 ha farm, valued at more than $70m, is also before the Overseas Investment Office. It is believed to be the second-biggest foreign acquisition of New Zealand land.