Rashford has already agreed personal terms with Villa for the duration of the loan.
The 60-time England international is currently earning around £350,000 per week at Old Trafford, where his contract is not due to expire until June 2028.
It is understood that Villa will cover 70 per cent of his wages, while the loan package will include bonuses for progressing in Europe and for qualifying for the Champions League again next season.
The 27-year-old has missed the last 12 matches under Amorim - who has questioned his lifestyle and commitment.
Rashford has been at United since he was eight years old and has never played senior club football for another team.
However, he is expected to wrap up a switch to Villa Park before Monday's winter transfer deadline.
Rashford - who has 138 United goals to his name after making 426 senior appearances for the Old Trafford outfit - said goodbye to his team-mates on Saturday.
The former academy starlet spoke to United staff and players at Carrington after being given the green light to prepare for his switch to Villa.
Villa's need for attacking reinforcements was sparked by Jhon Duran completing a £65m move to Al-Nassr earlier this week.
Duran was Villa's leading scorer this season with 12 goals.
Meanwhile, Ollie Watkins - who has bagged 11 goals this season - suffered an injury scare on Saturday night and was subbed off at half-time in Villa's 2-0 defeat at Wolves.
Rashford has not played for United since mid-December when he fell out with head coach Ruben Amorim.