As far as true renal phys goes, a person only needs 25% of total kidney mass to have a normal kidney profile. Assuming a person took care of hisself, all values should be normal.
However, that is rarely the case. Expect serum Cr values >1.5 as baseline in these people and everything else, expect for maybe filtration fraction, to be decreased (since it is a ratio of two things that are themselves decreased).
For boards though, you can be norma, functionally, with only one kidney.