Balde flew in from Portugal on Monday morning and his uncle Catio, who acts as one of his agents, said he hoped the deal would go through by Tuesday at the latest.
The 22-year-old, who has represented Portugal at U19 and U20 levels, started his career at Sporting Lisbon but was released without making a first-team appearance.
He gained experience on loan with Santa Clara in Portugal, Spanish side Badajoz and Cercle Bruges in Belgium before joining Guimaraes at the start of last season.
Balde played 27 league games in what looked like turning into only one season for the club, scoring nine times, and he had been linked with Crystal Palace, although agent Tommy Langley said that was never going to be a likely move.
"He is going to speak to Celtic and see where we go," said Langley. "He is very keen. You can see he has a scarf round his neck and he is a happy boy.
"Crystal Palace is a non-runner - never was a runner. There were quite a few other clubs in the frame but we are here at the moment and let's see how this goes
"He is a big strong lad, athletic, great touch, great feel and he is a boy who is ready now but who can only get better. You wouldn't want to pick him up from corners, would you?
Asked if the prospect of Champions League football was important to the decision, Langley said: "It is massive. It is a great stage. He is a very happy boy. We have a long way to go, let's see what we do."