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've only confirmed it with my current rent in Rockville and asked a few friends who rent to see, it was accurate, but again, I'm cautious.

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.

If I understood accurately as I described above, how did you write your lease agreement as far as what the LLC pays you each month. 

.$63k if you are accurate on your ARV...and that seems ambitious....you'll be $73k in plus soft costs...