We have several Photoshop users, two of whom would like to work part-time from the Home Office. Does adobe grant a second use right, so that we do not have to deal with any additional costs for new licenses?

Yes, Adobe grants, under its license agreement, the use of the license on portable or (!) home computers, as long as the software is not used on the main computer at the same time.

Source: Adobe EULA, as of Juli 2016