It's tenant occupied and not immediately accessible and we're deciding if we should accept a counter offer they gave us as a credit instead of repair.

I waited 24 hours and received a counter offer. 

So we did what you suggested: Since he asked to charge total $500, we counter-offered $250 and said that we don't need to see the receipts if it's that amount.He called back yelling at us, saying he called Pros and it's not possible to remove the stain.

@Evan Holly What was there counter offer??

. $325K Counter Offer for Purchase Price  (seller hasn't agreed to this yet it, is currently at $340K)6% Seller Contribution (seller hasn't agreed to this yet it, is currently at $8K)7.25% Rate20% Down$80K RehabRents $4.2K/monthTotal Monthly Expenses $2.8KCash Flow $1.3K

Don't rush to accept counteroffers.

A counter offer to someone who is interested in purchasing a property that has just taken a price reduction is more befitting.    

Do not expect a counter offer though if you are way under market (like 80%) and its not a real slow market.

A $250 grocery store gift card seems like a generous counter offer.

. - New roof, HVAC, pest/WDO mitigation, plumbing and some electricI have placed a counter offer based on these findings.