How to pull out money from a 2 flat that isn't your primary residence?

[Marcin Talaga]

A friend of mine owns a condo that is his primary residence.  He owns a 2 flat that he bought a few years ago in a very hot Chicago neighborhood and has gone up in value by almost $200k since.  He wanted to pull out some money to use towards buying another building.  His lender said since it isn't his primary residence he can't do that.  Does anyone know why?  Is there a good way to pull out money from an investment property?