But I feel like I would have to get on a bus tour with them to see the properties and areas in person. 

Just as an update, I met with the owner on this property and toured it.  

This was a bad idea on my part and I recommend all investors interview at least 3 property managers before deciding regardless of how you acquire the property (MLS, turnkey, off-market, etc).4) The staff at Zeker seemed nice and did provide a video tour for me before the property closed.

He now does the work of finding the arv based on comps etc; then we tour those which meet the basic criteria and I fill in rehab budget and verify the arv'sMy agent was very cooperative about doing the extra work, and we signed a deal a couple weeks ago on a sfh

I have had Realtors just give me codes to investment properties which makes it nice and easy to tour the property with no pressure.

I was beat out last month on a quad that received 25 cash offers in the first 24 hours.....no one was allowed to even tour the inside before submitting bids!

That says it all. l just estimated the amount of work it take based on touring the property. 

What things should I look out for when touring the house that are often hidden from the eye, but will be costly to fix?

Most average cities don't know what the hell they are doing or saying because they don't see ADUs except for 5x a year and simply deny them.My tour and research of a company called US Modular in California has the GC getting the feasibility study done for $3500 (used as a credit towards the build but is a fee if you don't move forward with build). 

Like yesterday's Tour de France stage being terminated early because of a mud slide from a freak storm.