just reducing the headaches of dealing with multiple vendors is (should be) enough to secure an account, let alone give a discount or freebie.
but as uncle phil sez, no giving away the farm either.
yull see under each of my posts where it sez, "multi services specialist" & "king of the upsell".
75% of my customers go with another of my services while i am there.
in todays economy, offering multiple services is the way to go, whether yer commercial or residential.
september begins year #34 for me and 33 of them have been multiservice offering.