Loan issues with credit unions

[Samantha Swenson]

We had met with a local credit union MULTIPLE times to discuss the best options for me and my husband to invest in rental properties.  Well we found a 4plex that we will move into one of the units and rent out the remaining units as well as our current home. We have the down payment and we end up cashflow off of the units so essentially we get to live for free with some money in our pocket. Well the bank just came back and said we need to ALSO show that we have 6 months worth of the amount of each rent in our bank account to now qualify for a loan....  I have never heard of this before! Why wasnt this explained from the beginning! I have researched rental properties till I've been blue in the face for the past 8 months and I have never come across this...... 

Did I miss something in all of my reading or is the bank trying to pull something on me... 

HELP PLEASE!