Is it permissible to sign a contract on a new house during the Three Weeks, the period between Shiba Asar Be’Tammuz and Tisha B’Ab?
Hacham Ben Sion Abba Shaul (Israel, 1923-1998) addresses this question in his work Or Le’sion (vol. 3). He rules that it is permissible to purchase a new home during the Three Weeks, including the nine days from Rosh Hodesh Ab until Tisha B’Ab, and even on Tisha B’Ab itself. Hacham Ben Sion writes that purchasing a home falls under the category of “Dabar Ha’abed” (avoiding a financial loss), given the likelihood that, especially in competitive housing markets, somebody else will buy the home if the purchase is delayed. Halacha therefore allows purchasing a new home, even on the day of Tisha B’Ab, in light of the financial loss that might otherwise be incurred.
However, one may not paint his home or have his home painted during the nine days from Rosh Hodesh Ab through Tisha B’Ab. Likewise, it is forbidden to purchase new furniture during the Nine Days, and one may not even place an order for new furniture that will arrive after Tisha B’Ab. Painting and purchasing furniture is allowed, however, before Rosh Hodesh Ab. Furthermore, a synagogue may be painted even during the Three Weeks. And if the price of new furniture will be higher after Tisha B’Ab, then one may make the purchase during the Nine Days, given the financial loss that he would otherwise incur.
Hacham Ben Sion rules that one should even refrain from purchasing books during the Nine Days if he does not need them for study during this period. Books that one wishes to purchase for general reference, or to use at some point in the future, should not be bought during the Nine Days, but may be purchased before Rosh Hodesh Ab.
Summary: One may purchase a new home during the Three Weeks, the Nine Days, and even on Tisha B’Ab. One may not paint a home during the Nine Days. One should not purchase or even order furniture during the Nine Days, unless the price will go up if he waits until after Tisha B’Ab. One should not buy new books during the Nine Days if he does not need them until after Tisha B’Ab.