You should be able to invest with the female orc with the Imperial apprentice, but not the male orc who is the Jarl's personal smith.
According the bug list on http://www.uesp.net/wiki/Skyrim:Ghorza_gra-Bagol#Bugs you can't normally invest in her shop. (unless on PC with the Unofficial Patch)
I know in the PS3 she could not be invested. Had the lead into dialog but I had nothing to agree with the investment. Honestly have not tried on the PC with unofficial patches yet.
That comment on the UESP is correct, Ghorza gra-Bagol cannot be invested with due to a bug. There is no way around this issue on consoles. The USKP does fix this issue though for PC users.
So I thought. The same thing occurs with an XBOX360