Think this is the year San Antonio's multifamily market will hit the pause button? Don't count on it. The city is off to a strong start with double-digit increases in the rental rate growth for one- and two-bedroom apartments, and according to Zumper's National Rent Report, those one-bedroom units have hit the average $900-per-month mark — a milestone the city has been flirting with for the past few months. San Antonio took 49th place among the most expensive rental markets in the nation, which…