Sinclair remains the only New Zealander to ever score a double century on debut, smashing 214 against the West Indies in Wellington in 1999.
The lanky right-hander managed another double ton against Pakistan the following season but never cemented a spot in the Kiwi team, appearing only sporadically until his last Test in 2010.
At 37, Sinclair, who has a wife and two young children, said he could no longer rely on income from playing for the Central District Stags during the summer, then looking for casual work in the off-season.
He said prospective employers were reluctant to take him on when they knew he would be unavailable during the cricket season, so it was time to look for a long-term career.
Until then, Sinclair said he would have to sign on for the dole — a stark reminder that not all promising cricketers go on to fame and fortune, particularly in a small market such as New Zealand.
> Sinclair remains the only New Zealander to ever score a double century on debut, smashing 214 against the West Indies in Wellington in 1999.
> Sinclair has played 33 Tests with an average of 32.05.