The 6th loan, how do you get it?

[Cali Skier]

So my wife and I have 4 loans.  1 for our home and 3 rental properties.  We want to keep buying properties but have been told that after 5 loans it can be difficult to get a 6th loan.  

Here are my questions...

1. We want to get a loan to make an addition to our current home.  Would that be considered loan number 5?

2. How do you get the 6th, 7th, 8th, etc. loan?