CAP rates are generally used only for commercial properties, so you can compare different returns based on two completely different types of commercial properties.  

I found several online but I don't know how to compare them.

Ask the agent for comparable properties.Just a few ideas to consider.

and comparing it to NOI... eeeehhhh I'm pretty sure that you're $275k more in debt than you otherwise would be, so you need to factor that in.

Is it as easy as estimating ARV through comparable sales, or should I downward revise ARV ~10% to be conservative?

the bright side of finding BP after you've already had a deal is that you can focus and have a frame if reference for the info you get, compared to your previous experiences.

Two of our contractors spring to mind, the plumber who despite all the best connections in the world hates the business of rental property, and our tree guy who plays the same game as us (buy and hold) and we often compare notes.Some people like the game, some don't.And again, the debt thing is down to personal choice, although interestingly a friend who spent $65k on a truck has since told us that it's the last time he's buying such an expensive item, and when it's paid off, it's paid off.

I personally believe that IRR is a far superior metric compared to commonly used real estate metrics like cash flow, CAP rate, and cash on cash.  

You need to look at warehouse comparables in the area listed for sale and solds to get a cost per sq ft.  

Consider vacancy rates and look at the historical appreciation of rent in the area.In Canada very few markets support good cash flow comparable to the United States, but we still have thousands of very successful investors who make due in every market.Do what's best for your future.