Is zakat obligatory on a cell phone store that was purchased for 58,0 riyals as "khalou" (key money), with a net income of 1500 riyals per month, given that the family has debts, and if it is obligatory, how much is the zakat estimated to be?

Zakat pertains to goods purchased for sale, not to the premises [shop] itself. Its hawl (one-year period) begins from its origin if purchased with wealth that already reached nisab (the minimum threshold for Zakat liability). Otherwise, its hawl begins from the time of purchase. Upon the completion of the hawl, the goods are appraised, added to the cash, and any debts are subtracted. One-quarter of one-tenth (2.5%) of the remaining amount is then given as Zakat, provided it reaches the nisab (equivalent to 85 grams of gold). If it was not paid on time, it should be paid now, with an effort to determine the value of the goods on the day the hawl was completed. A condition for deducting debts is that the Zakat payer does not possess other non-Zakat-eligible wealth sufficient to cover the debt. There is no Zakat due from one who does not own the nisab, nor on rental income unless a hawl passes over it and it reaches nisab by itself or by being added to other cash and remains at that level until the end of the year.