Everyone loves a holiday giveaway, and savvy condo buyers can score one if they know what to ask for during sales negotiations.  Concessions around things like free rent are common in the Boston apartment market: Zillow reported nearly 30 percent of apartment listings in the city in October came with a freebie like waived parking fees or several weeks of free rent — a 7.4 percent increase from a year ago.   Read the article…………………………….