Maintenance varies greatly based upon a number of factors. Maintenance consists of 3 things: your share of the underlying mortgage, your share of the real estate taxes and your share of the upkeep of the building. If there are many units, more of you share these costs than in a smaller building. The amount and terms of the underlying mortgage are a factor, as well as how many employees are on staff and other operating costs.
As far as a fair offer, I can't answer that based upon just knowing the asking price, because I don't know if the asking price was in the ballpark, or too high or low. To bid correctly, you'd have to know the current comps, particularly the recently sold. A fair offer is what is fair for this market, not a percentage off of the asking price, because the asking price could be off. A good agent can do that research for you.
Halstead Property, LLC