Due Diligence question

[Jason Leak]

Hello BP Family,

I am looking to get advise on a CRE due diligence issue that pertains to negotiations. Here are the specs:

6 unit brick multifamily Apt building-priced at 569,000- negotiated down from asking 600,000

6-2bd/1bth apts currently does 4700 per mth-rent currently about 20% under market 

at the start of due diligence was 100% occupied-That is what I based my offer on building performing at 100%

tenant just gave his 30 day notice -so before closing the building will have 1 vacancy performing at 84%

The inspection also turned up 15k of safety violations 

I believe both are points of renegotiation-I'm just not sure how much is my question

-I was going to ask for 15k of a closing concession to cover the safety issues

-but how much is considered acceptable/reasonable to decrease the price for the vacancy? If I am correct on this point.

I am looking forward to the communities responses and thanks in advance for your assistance and advice.