Offer 55k and see if they counter offer.

There are several others that have come up recently that we might be interested in.The bids we have placed are pretty much our best and final bid so counter offers will most likely not be accepted by us.My question is how many bids is safe?

Still awaiting rent rolls before I make my counter offer.

If you have access to the ducts, replacing them is relatively easy or get an estimate from an HVAC contractor and factor that into your counter offer. 

I am seeking anyone's insight on how should I counter offer the proposal.

Your counteroffer was extremely reasonable.

Perhaps look at this counter offer as a way to tie up the property and then look for the capital, rather than vice versa.

The seller have had this property listed for 1year and 1/2 started at 258 they reduce aBout 6 months ago to 190 I lowballed themAt 140 they felt offended counter offered at 170 I said ok  made sense for me .. then when the realtor became aware I had my own realtor he says the people pushed back and want 180 I said ok now he says they want 188 and they considering going up to 200 ( huh)  I'm considering walking away from the deal I wanted the property to open a restaurant  but this realtor is becoming difficult and he is a joke 

The seller returns and counter offer it.

So for the short answer, you can negotiate...to an extent.As far as what documents are required, you will need to provide income documentation (tax returns, pay-stubs, P&L if self-employed, etc), identification, and purchase documentation (purchase contract & counter-offers).