Or the person who tries to negotiate a bulk rate discount, cops an attitude, and fusses about my attitude, and threatens to rat me out to my broker or the ethics board if they don't get their way?

Also you can always inquire about the other buildings and they may be willing to give you a discount on a multi-purchase situation.

You find a property at an extreme discount and you find a buyer who is ready, willing, and able to buy that property at a slightly less of a discount that you bought it at.

I use software I designed for this purpose so I'm consistent and fast.

Account Closed funny enough I already use skip tracing software.

They would pay 500-600 a month and possibly manage the property for a rent discount.

Which basically means if you are looking for a discounted off market property, then some of your discount you were hoping to obtain just went to the agent.

It's up to the Seller to prove otherwise.Additionally, low/no down payments are normally used for distressed properties that are discounted below market value.  

Some "wholesalers" actually tie up properties on the MLS trying to "wholesale" them when there is no legitimate discount off of FMV.

Most of the big players use some sort of software called underwriting desk or something and if you fit nicely into their lending model then it spits out an approved.