However, were I to do it at a charity fundraiser or the like, it would fit perfectly as long as it didn't come off insincere.

You are either running a business or you are running a charity.

Aloha,Decide if you are running a charity or a business, and operate as such.

Payments by ACH are subject to the ACH network operating rules of the National Automated Clearing House Association or NACHA, which permit the initiator of the ACH payment for up to 60 calendar days after payment to claim the transaction unauthorized triggering a return of funds, i.e., an ACH chargeback.

You are not a charity and you cannot help everyone.

It's a business, not a charity, right? 

You are not a charity, they don't deserve to pay half market value.

I do not rent to folks with a history of evictions, their income must be 3 times the rent and verifiable, etc.Then she said that I only care about money, well yep, its a business not a charity.

I have 6 tenants, though one is on financial assistance with a charity (not S8). 

The GC isn't running a charity and neither should you be.So if you told them or had a contract with them to do it at cost (without any stipulation as to what cost truly is) you would probably be able to argue that you should get the actual true expenses plus some admin fees and your time on the job without profit.