How accurate is the $220 for operation cost?

Not sure how accurate that is.I would look to learn as much as possible on BP etc and just start righting questions down and grasp the understanding of the businessAlso don’t believe people when they say this business is all rainbows and unicorns.

As a professional, a contractor should have a reasonable idea on how long a job will take and the cost of materials..... not exact, but a reasonably accurate idea.

We are buying each home for $148,000, with $500 in earnest money, and the Zillow value (which I realize isn't super accurate) is about $165,000.  

For the HELOC - I was told by both a mortgage company, and a local bank, that we'd need to own the property for 1 year before refinancing - but seems that may not be accurate.

If your numbers are accurate, looks like you have a good deal there to own a primary home with equity in a short period of time.

If those two things are not accurate and they weren't all cash offers and maybe the home wasn't being sold "as-is" the obvious answer would be that things came up after mutual and the Buyer was able to negotiate the price down due to maybe an inspection or something else that may have come up during a due diligence period.

A well-kept, accurately-priced house will sell quickly. 

You need an agent to give you accurate comps, you need a contractor who can give you a good repair estimate, you need someone you trust to go on the appointment for you and meet your seller and put the property under contract on your behalf.

I just realize how incomplete the data is on these sites though and am wondering if there are tools or sites that have more complete and accurate data.