Is the similarity of economic condition one factor on friendship? My answer is a "Yes". Those people who have similar wealth usually share their lifestyle and ideology, which may contribute to the establishment and maintenance of their friendship, although we also need to keep in mind that the shared economic condition is not the only determinant in this issue.

The establishment of friendship often relies on people's similar lifestyle. People often need an opportunity to start forging their friendship, and this often happens if they fall into the same social category. It is highly possible that the people who have similar money go to the same bar and start talking, as opposed to the people who have different wealth. For instance, middle-class workers must go to different places for entertainment from the low-class ones, reducing the probability of creating friendship between the two classes.

Another issue associated to the similar economic condition is the fact that people who are similarly wealthy often share similar ideology and interests. As we all know, it is tough to remove the predetermined prejudice and hostility between different social groups, and even worse, they often don't try to suspend the hostility because the expression of the ideas acknowledged by their group can enhance their identity. To narrow the gap between disparage ideas is not as simple as we might suppose. For instance, middle-class people often have an interest in the value of historical heritage, while low-class people may barely have the energy to feed themselves; therefore, beyond any doubt they cannot create a conversation around either how to travel or how to survive if the two types of people meet on occasions. They don't share their interests.

But I am not arguing that the similarity of economic condition is the only variable in this issue. Obviously we are aware of many commonsense and famous cases in which a wealthy person and a poor one forge a sound friendship because of their shared ideology or interests. We can take two economists as an example: when Coase first arrived at the USA, he was very poor because he didn't have a official PHD degree for the application of any faculty position in the US, but Friedman, who was a prestigious economist at that time, knew the Coase's ability and they were quite great friends. The reason is that they shared a similar focus and they both appreciated the counterpart's argument even though their opinions often conflict with each other.

In conclusion, similar economic condition is an important facter in terms of the establishment and maintenance of friendship, but it shouldn't be seen as the determinant of this issue.