When I lived in an apartment, I tipped front desk $100 for full time and $40 for the part time people. Maintenance was $100 for the team since I tipped at point of service. Especially when it was something dumb I'd done.

For a co op, I'd say go in as a group as someone suggested. Saves the stigma of who didn't tip for whatever reason and while a bunch of $50 envelopes is nice, $1000 cash is nicer.