The article suggests a method of economic advisability calculation of purchase and reconstruction basement-level rooms without application of expensive technologies and equipment. The method includes estimation of structural elements physical wear-out of the building by means of visual overview, preliminary possibility evaluation and penetration cost, building of additional exit. Special attention is given to construction of additional exit. The article suggests a fast and, more importantly, a cheap method of calculation advisability of investing in basement-level rooms with area up to 100 m2 and more. The method is especially recommended to investors, who participate in real estate auctions, when the number of real estate objects to let is big, while the time frame is tough. In such case, it is suggested that the investor applied as cheap and fast method to calculate advisability of investment as possible. It is important to stress that the method suggested in this article is only a method of preliminary calculation; it allows investors to roughly assess investment attractiveness of a room, and to select rooms that require to be surveyed further.