Install of a Full Air Conditioning System In House With None

[Kenneth Picha]

Hi,

I wanted to find out if anyone has a rule of thumb when estimating on the full install of a house that needs an air conditioning system in the house.  The house was built in the early 1900s and has the old octopus heater type system.  I wanted to find out to get a rough estimate before I get it under contract.  Yes I  know I will get a professional's estimate but any rule or thumbs or good estimates will help with my negotiaions.

Ken