Rental increase for adding a washer/dryer

[James Leahy]

I own a two family townhouse.  The tenants have asked if it is possible to add a washer/dryer in the basement for both units to share.  What do you think would be a fare rental increase for the installation and use of a washer/dryer? 

The first unit has only one tenant and the second unit has three tenants.  I would need to spend about $800 total for the equipment and installation of a dryer vent.