In almost all cases the fee is paid by the client. The fee is is based on the overall value being brought to the relationship including but not limited to finding the best possible rate, points, maturity, structure, covenants, closing costs and terms.
For indicative purposes the fee often comes out to be close to 1% of the loan amount.
This fee is paid once at the time of loan funding even though the client will benefit from the savings on the rate year after year.