If you make a low-ball offer you won't even get a counter offer in a hot market.
Unless the contract says 'as is' everything is up for negation. Even then, the buyer usually still has the right to ask for repairs or back out of the contract.
The seller can try to negotiate with his or her agent for a lower commission if you don't have an agent. But they aren't obligated.
In a slow market you want to price to sell. If you price too high... you'll knock yourself out of the running.
In competitive markets where two offers are presented to the seller, the one with 20 percent down looks better than one with a smaller down payment. But sellers still tend to drift toward someone with a larger down payment.
