I have had this happen in our new location. Several of the other
businesses wanted to access our wifi since it's by far the fastest and
best in the building. I actually turned them all down even though some
were willing to pay. Wifi is our most prized "physical" amenity and
without it we wouldn't exist. I chose to preserve our bandwidth and
security by not opening it up to non-members.
As for your shitty landlord--consider moving when your lease it up. We
had to move b/c of our crappy landlord and even though the move was
expensive and time consuming we're 1,000 times happier to not see his
face every day. Our new landlord is incredible!
Angel