Converting multi-family to pet friendly

[Rich E.]

I have an 8-family apartment building and currently do not allow pets.  While I am not having any trouble finding tenants, I have noticed that even though my ad says "no pets", about 70% of the calls I get are asking if I will accept a pet.  I am starting to see this as an opportunity to get more tenants and increase my cash flow with pet fees.  

Does anyone have experience changing the pet policy for an existing multi-family?  Was it worth the hassle and damage?  How did the existing tenants take it?