But apparently the majority of this building is already sold out, with over 50% of the units being investors.I sent an email to the agent that had taken us through the presentation - and she agreed the numbers were likely accurate but I should be looking at this with a "long term view of the price appreciation and someone paying the majority of my rent".I'm wondering what the consensus is on 1 bedroom condos for renting, and the idea of negative cash flow? 

Banking on appreciation is gambling.

I’ve recently been searching for a system that provides good, accurate, presentable comp data for commercial sales...

You really need to check multiple sources to get an accurate gauge of what's appropriate for your specific property/area.Here's an article with a bunch of resources you can use to help get an idea of what your property's rent should be: How to Determine Fair Market Rent.

More general question is HOW do I accurately find out what the cap rate for an area/property should be?

@Lisa Ramos if your numbers are accurate, then investing the money to bring the house in line with the current market makes sense. 

Also recognize there is an inherent problem with getting accurate numbers on small properties. 

A few books I was considering sadly don't have a vey good rating on fakespot (though not sure how accurate their review system is).  

Is it accurate?

Some folks are willing to take the risk in the gamble for appreciation, especially here in CA, they are typically purchasing when the market is down, not high as it is now.