The 45-year-old is in his third managerial job having won promotion with St Johnstone prior to being lured back south of the border to take charge of Bristol City in 2011.
McInnes has just returned from a three-week holiday in America following an impressive season which saw Aberdeen finish runners-up to Celtic in the league and both domestic cups.
The Republic of Ireland worldwide is keen to move to Parkhead and is expected to go for his medical today.
And Bain has told his new manager around £20m of the money made from player sales will be handed over.
The offensive brand of football that he has introduced to the club has made them the nearest challengers to Celtic in recent times, albeit still several points behind them in the final league table last season.
McInnes is believed to feel that he has taken Aberdeen, who have lost their former captain Ryan Jack to Rangers and are set to see several other first team regulars depart, as far as he can.
David Moyes left Sunderland nearly three weeks ago and chief executive Martin Bain has taken his time over appointing a successor. He has also received glowing recommendations from Walter Smith and Graeme Souness.