I’m not sure on the details, but sometimes locks can be re-keyed. I think that means they just change the cylinders and keep the rest of the lock body.
Anyway, my brother had that done once (messy divorce) and he said it was a whole lot cheaper than replacing the locks. So you might suggest your friend ask the locksmith about that.
StarvingButStrong, was your brother planning to replace the locks himself, or have a locksmith do the work? I’m having trouble, here, believing that having a locksmith rekey all the locks in a residence would be cheaper than replacing said locks DIY.