Ian Craigie, 63, a retired barrister who taught at St Ignatius' College, Riverview, was reported missing when he failed to turn up for work. He was found dead in his Glebe flat three days later, on September 24.
Yutian Li, 21, has been charged with his murder and accused of using Mr Craigie's keycard to withdraw thousands of dollars from ATMs.
He was refused bail and remanded in custody to appear in Central Local Court on Tuesday.
It is understood Mr Craigie met his alleged killer at Central railway station and that they had met several times before.
Detective Inspector Peter Bailey, crime manager for Leichhardt Local Area Command, said: ''We believe Mr Li was known to Mr Craigie. We believe he may have known him for up to 12 months but the relationship of both people is still unconfirmed.''
Last week friends and colleagues of Mr Craigie were mourning the loss of an intelligent and popular friend and teacher.
Shane Hogan, headmaster of the 129-year-old Jesuit college, said: ''He was a part-time teacher of classical Greek at the school. He was a very good teacher and well respected.''
Mr Craigie was a barrister and had worked for years with the Commonwealth Department of Public Prosecutions until his early retirement at 55.
Lawyer Peter Mollard was a friend for more than 30 years.
''He was just a delightful person, highly intelligent and with a huge range of friends,'' Mr Mollard said.
''He had a passion for classics, it was his passion in life and he was doing a masters at university in Armidale.''
Mr Craigie's memorial service will be held at St John's Anglican Church in Glebe on Tuesday at 11am.