The only expense you do not use is your mortgage payment (principle and interest), because we are looking to see how well the property would perform if you buy it "all cash". 

As a local agent who specializes in multi family purchases, I have echoed many of the same principles to my clients.

One of the core principles is that you can't be involved, do anything yourself or pay with your personal money.

I assume this is a cash deal so there is no lender to object to this exception.

So if it looks interesting and in line with your objectives, dig deeper and verify your numbers and complete your due diligence.

If we bid our own principle do we have to pay that out of pocket?

It was a targeted purchase using the principles laid out in HOLD: How to Find, Buy, and Rent Houses for Wealth.

I would be interested in discussing your 'options' for doing one or more "rent to own" lease purchase agreements with existing and future tenants and tenant buyers, particularly since you can also then 'resell' 50% (or up to 3/4, if that's your objective?)

Success will most assuredly follow in multiple ways for those ready to apply these timeless principles. 

You can signup at his site, principles dot com.