There is not set rule on how much a wholesaler can charge since they are not licensed :) but I would say $5K is more fair for that price point. 

He's only going to charge for materials and any labor that he has to pay someone else.

As I said $7500 is not high compared to what others are charging.

That is a great way to be in real estate without all of the hassles, but still making 8% or 10% or whatever you want to charge.

Calculate how much extra this tenant's habit is costing you and factor it into the rent or add an extra charge for excess utility use.

There is also a cash out charge that FNMA/Freddi Mac cost.

Now here in the north west we have HML that will put up 80% of the auction price and take security in the trustee's receipt then do the loan when the deed comes. they charge 4 points for this service. 

They will probably just charge you a few hundred bucks to do so.

Could this have an impact on what RE agents charge?

You should charge extra for the parking spaces, and make them private.Looks like the average unit there runs about $700/mo, so yeah, I'm say you're substantially under market.