Negotiating my first deal

[Quadeer Porter]

Hi everyone,

I'm negotiating my first real estate deal currently. It's a two family home, 3,120 square feet, with three parking spaces located in East Orange, New Jersey and we have it under contract. There are currently tenants in the unit, but they will be vacating it after we close. The owner wanted $274,000 for the house, but I negotiated him down $250,000. I'm funding this project using a 203k loan.  

After the inspection, we discovered mold, both the water boilers needed to be replaced, the heating using was actually improperly set up, and the oil tank is still on the premises. The heating unit is currently pumping out unhealthy levels of carbon monoxide and dirty air into the house. My lawyer has sent a letter to the seller telling him the unsafe conditions of the house and that the tenants there should be evacuated immediately due to the health risks. 

As you can see, this is a complex project. For the most immediate repairs, my contractors said it will cost $15,000, so that's what I asked for as a credit to the seller. 

Any tips on how I can negotiate the best value for this deal? The appraisal will be happening in another week. 

Should I hold off being too pushy with a lower price until the appraisal happens and base my goal price of the house on that? Or should I try to get the cost as low as possible in case it appraises for higher than I expected which is over $235,000?