What neither of them answered was the costs of adding the units; I have done a few flips in the area and have noticed that the bids depend on a few things:1) how big of units do you need (you probably need 2 of the smallest units honestly)2) is the duct work already ready for the units?

If they make ARV claims, make them provide WRITTEN bids from licensed contractors4.

Get 3 bids from reputable contractors, and they can give you an estimate of the costs involved in this. 

If you're talking about an "opening bid" amount on an auction site, it means nothing, it's just a teaser.

I am planning to bid on a sheriff sale property (for personal use ) in the coming weeks. 

I was happy with the work they did.However, I'd still always recommend getting a couple of different bids.

We bought a house in Marin a few months ago, we had 5 contractors come out to bid on some minor kitchen work we wanted to do.The General contractor we chose seemed honest, trustworthy and came highly recommended.

Any recommendations on contractors for bidding?

to walk the property and develop a bid for all items that need repair/upgrading. 

Any other advice or clues to look for beyond a normal walk through and a normal bid?