Have applications available along with the written criteria you will use and documents they must produce for them to be accepted. 

But, the truth is you don't really get to determine the wholesale fee: Your seller and your buyer do.Wholesale fees are not set; they are earned.The most you can charge is whatever still allows your investor buyer to make an acceptable profit.

This is a people business, so network and develop your social skills.

I offered $52k and seller accepted, multiple contracts fell through already, I was told.

Payoff is more than the house is worth, so had to negotiate with them to get them to accept less.

Social media8.)

Should I avoid lowering out of that range to encourage acceptance of my terms?

Accepted the request. 

Let him know that it is not acceptable to do this very often though. 

No personal story , makes you seem desperate, stick to the facts that you have money and you can pay x amount of dollars and ready to proceed with purchase if offer accepted!