Agree on THAT-clause

[vien_phan]

Agree /i/ipr/it/tf/tw with sb about/on sth
with sb about sb
with sb
ex they agree with him on buying this house.
they agree (with him) (about/on) what he did to her.
they agree (with him) (about/on) where to business.
reading some grammar books, I see some authors use preposition before Wh-clause like these:
ex
they agree with him about/on where to business.

Agree ( ipr) wih somebody about/on something, something here I replace by THAT -clause.
ex:
They agree with him about/on that his buying this house is right.

is my sentence like that right or wrong?

[Casiopea]

Try,

They agree that buying this house is right.