1) From the beginning of Av we decrease happiness. We also decrease business dealings. There are those who contend that this applies only to acquisitions for happiness (like for a wedding etc.), and others say that one must minimize all business dealings. Everyone agrees that if there is a sale or a special offer etc., that one may buy. (Shulchan Aruch and Mishne Berurah 551)

2) Similarly, one must reduce buildings of happiness. This refers to any building which is not directly for living quarters itself, but is done for profit. (If one has hired a non-Jew on a contract with a fixed price before the first of Av, and he decides of his own accord to work even on these days, it is permitted. It is a good thing, however, to give him a small payment to make him wait until after the ninth of Av.) (Mishne Berurah ibid)