Denver- Garage with unit above to rent out? How much?

[Samuel DeMass]

I have a friend looking to purchase a home in Denver and they heard they can add a garage to the property with a loft attached.  According to the realtor, the laws recently changed to allow the expansion.

1.)  Can anyone verify this change?

2.)  Any guesses at a cost range would you be looking at to build a single garage with a loft above to rent out?  Has anyone done this?  What was your experience?

Thanks BP!