If it's for work or casual use, no way! Borrow or rent designer bags for what? To show it off? Or let others think "Oh, look I have a designer bag and it's authentic!"? However, if I will be attending a formal event and I can't find/don't have enough time to find/can't afford to buy a purse/handbag to pair with my dress, I would probably borrow from a friend pero kana kung emergency na jud kaau. I haven't tried it though.