In the previous Halachot we have explained that one must minimize business transactions which bring about joy from the beginning of the month of Av until the Tenth of Av.
Maran Rabbeinu Ovadia Yosef zt”l writes that one should refrain from purchasing gold rings and other jewelry during this period, especially when a groom is purchasing these items for his fiancée, since this brings about feelings of joy. We were asked if a salesman who sells jewelry in his store may continue to conduct his business during this time or not. Maran zt”l already discussed this issue and writes that salesmen may sell gold and jewelry during these days since there are way for people to purchase them in a permissible manner, i.e. when this is not being done in the context of a bride and groom. Additionally, there is even more room for leniency based on what the Rama writes (at the end of Chapter 303) that nowadays, jewelry is not as special and rare as it was in previous generations, thus, purchasing them does not cause any unique joy. Thus, although we have written that it is forbidden to purchase jewelry when it gladdens the heart, there is nevertheless room for leniency regarding the salesman.
It is permissible to buy Sefarim (holy books) during this period since this constitutes a Mitzvah and there is no custom forbidding this at all.
Maran zt”l writes that it is permissible to have renovations done to or extend one’s home during this period if the family is large and it is difficult for them to live in such cramped quarters. However, when this is just being done for luxury or aesthetics, one should not renovate the house in any way during this period.
It is likewise permissible to move into a new house during this time, if this is being done out of necessity and not just for comfort or convenience. In this case, it will likewise be permissible to hold the customary “Chanukat Ha’Bayit” during the Nine Days as well by inviting ten men to come to the home and study Torah and reciting the customary texts after which, some light refreshments may be served. The remainder of the housewarming celebrations should be postponed until after Tisha Be’av at which point the owner of the house should wear a new garment and recite the “Shehecheyanu” blessing on it.
Contractors who build houses during this time may carry on with their work since there is a housing shortage in our generation and this does not constitute “a joyous form of building” which is prohibited during this period. There is especially room for leniency in Israel, for building homes in the Land of Israel in order to inhabit it is a great Mitzvah. (Chazon Ovadia-Arba Ta’aniyot, page 168)