So, if come closing it was not vacant, the parties could negotiate something such as a price reduction for taking on the headache of eviction or the buyer could terminate the agreement for nonperformance and get the EMD back.

Also have a contingency plan and risk reduction plan.

Nobody wants to lose any money, but losing $5k or $10k is a much easier pill to swallow than losing 50k or 100k.

You can probably search the bigger pockets website for attornies that work with investors in your area.If the numbers on the deal barely meet your investment target then consider hiring an attorney to work with the estate and see if you may be able to get an additional reduction in price.

@Christopher Phillips   maybe i'm reading this wrong, or it works differently in NY, but a 6% seller concession normally means the seller is giving the buyer 6% of the purchase price to use however they want in the transaction - be that for closing costs or principal reduction or down payment, whatevs.A seller typically doesn't have a say of what can and can't be included in the borrowed amount, that's up to the lender and the loan program. 

He is wondering if he should take the 300k as a price reduction (leading to boot from 1031 as he does not want to go higher than 25% down payment) or if he can avoid boot by keeping the price the same and take the 300k in a capex escrow account with the title company to be used for repairs over the next year (title company and bank are ok with this).

In essence you have to prove your house isn’t worth what they say it is worth – and since they started 15% below market – you have to be able to justify the argument that your house is worth (say) 25% less to get a 10% reduction in your taxes.  

My plan is to allow my portfolio to compound, and then after college pill up some money and start investing in real-estate.

Not including the principal reduction & tax benefits in your "flow".

Yes, you read that correctly, the appeal can go either way or stay the same, you lose if the taxes go up.My brother appealed taxes on a house in Philadelphia and got a 12% reduction using the guy below:Jerald GoldfineRE Tax Associates of Pennsylvania LLCGood luck.