How reliable will they be in conducting the physical, financial, and legal due diligence? 

@Rob Drum is a very reliable source of Bham info. 

Does anyone have a referral for a reliable handyman/woman in the St.

I feel like thats a more reliable way to add value, as long as their track record proves they have performed that in the past of course.  

Someone reliable should at least have a website.

However, the drawback to this is a markup on all the fees, unless you were to find a reliable contractor yourself or you did some of the work on your own.

The most critical piece of the puzzle to have reliable "boots on the ground".

I'd like to ask fellow investors how to build a reliable cash buyers list quickly?

No, the only reliable way to avoid this particular hustle is if you know something about furnaces, have someone who knows something about furnaces on your payroll, or have carefully worked to build a long-term relationship with a local reputable HVAC outfit, typically over years.

But I'm having trouble finding a reliable Real Estate Agent in my area who is investor-friendly.