It appears that buying an older domain might help you in some ways. First of all, it is supposed Google already indexed it so you don't have to wait for that anymore. Its ranking can also be higher. It is also supposed that the domain surpassed the test of time, in other words, if it still exists, it might be trustworthy. But, you have to be careful not to buy an old domain that was used for inappropriate business, such as adult sites that have a spamming history. This can bring upon you some Google penalties.