Malls, apart-hotels and business centers are growing like mushrooms. So naturally, there is competition to attract investors. The biggest attraction is, of course, steady rental income, and 7-10% is a huge return by any measure. So what's the catch for builders. Well, they must've build this cost in the price, second, they'll look to higher rental yield for themselves after completion, and third, this reduces their marketing cost, which sometimes runs to 20% of booking price.
As a matter of fact, high-end commercial projects give huge returns to the builders. So giving rent to attract buyers is not impossible. There are different techniques, for example, in Dubai they give you possession in 1 year for a 3 year payment plan.
So I wouldn't completely rule out such options, specially, if the builder has a standing and proven record of successful projects.