This would appear to indicate that the institutions are becoming a much larger share of the total bidders. 

Is there any specific bank or lending institution that is best or is pre-approval the same all accross the board?

When I was trying to finance a multi-unit recently, I found that each lending institution has a unique set of internal rules in addition to the federal regulations.  

Can someone suggest a financial institution to refinance an apartment building.

At minimum, I'm sure it's true for that institution. 

According to this article, if I apply within 14 days to each institution, it will only cost one inquiry.http://themortgagereports.com/413/credit-check-fico-mortgage-ratesBut do the same guidelines apply since I am an investor and not a homeowner?

Looks like you would benefit most from an institution that offers the biggest ease of use online and with limited fees associated with it.

And as for being an REO listing broker, the lending institutions decide who to use based entirely on production and success.  

Their service is usually much better than the large banks and often their fees are minimal compared to the large institutions.

Also, if he is an individual and not an institutional hard money lender, he could make up his own terms.