When the potential buyer or seller is convinced that they have found a friend in you, it will be much easier for them to state reasons for objections to the sale. This person might say to a salesperson that they don't want to buy because it's too expensive, or they may not give any reason for their objection. This means to get the sale, the salesperson must either drop the price, get pushier to try to find out what the objection is, or give up on the sale. Be a friend when selling, and you'll be given the opportunity to answer those objections. This technique alone can save you time and money on a large scale.
People hate or fear a salesperson.
All they see is someone trying to get their hand in their pocket. However, a friend, especially one with common interests, who thinks like them, is someone to be trusted, and advice to be taken.