Sky Sports:
It was during loan spells with Bristol City and last season with Wrexham that Foster showed his true credentials.
Now a deal understood to be worth over £1 million is in place.
Foster is expected at United's training complex at Carrington over the next 48 hours to complete the formalities.
"Ben is delighted that a deal has been agreed," confirmed Foster's agent Lee Payne to skysports.com.
"He will now look forward to talking to United.
"It is a dream come true and he cannot wait to meet with Sir Alex."
His agent Lee Payne:
"Sir Alex Ferguson has been keen on Ben since he watched him play for Wrexham in the LDV Vans Trophy final last season.
"He sent his goalkeeping coach Tony Coton to watch him play for Wrexham several times last season and was very impressed.
"I think Sir Alex's son Darren also mentioned to Sir Alex how good Ben was as well. We've agreed a deal and now it's case of Ben going to Carrington to agree personal terms and pass a medical."
And Fergie is keen to ensure Foster's progress continues this season by farming him out on loan to an as yet unnamed Championship club.
"That's the strategy," confirmed Payne.
"To get him out on loan for one or two seasons and then, at the age of 24, to take over from van der Sar when his contract runs out.
"Playing in the Championship will be another great opportunity for Ben to show what he can do. The lad's potential is frightening."