Villa are expected to double the £9 million they paid Watford for Young four-and-a-half years ago.
United and Villa have been in talks to try and complete a deal for the England player.
But it is understood the finer points have still to be thrashed out and that may mean the transfer not going through until after Young has tied the knot in his native Hertfordshire on Saturday.
Young indicated after England's Euro 2012 qualifier with Switzerland on Saturday that he wants to play Champions League football.
He has only 12 months left of his current deal at Villa.
Villa - and the then manager Gerard Houllier - had been braced for the possibility of losing Young after he shelved talks about any possible new contract.
His departure follows on from the loss of other leading players in Gareth Barry and James Milner to Manchester City.
Of more concern to Villa - in addition to appointing a new manager - is trying to ensure they keep hold of their other star winger in Stewart Downing.
He has two years left of his contract but has also shelved talks of a new deal and has been linked with a move to Liverpool.
Source: PA
Source: PA