We could always try justifying why you'd be currently living a street lifestyle for a bit. For instance, your last run before campaign start went sour, and you've spent the past 3 months hidden in a bolt hole half a continent away from your usual stomping grounds. You got three shirts, a pair of pants, three pairs of socks, three pairs of underwear, a knife, a pistol, 40 bullets, an armor jacket, a burner 'link and 317 nuyen to your name, since that's the sum total of what was stashed in the bolt hole, plus what you didn't have to leave when the run went sour. Last week, the coffin hotel kicked you out, so you're pretty desperate for a run to get back on your feet and start establishing yourself in a new city.
Remember that one of the core assumptions is that most shadowrunners are SIN-less, and it really sucks being SIN-less. I'd wager that in-universe, it's the minority of runners that can afford a stable lifestyle of any sort, much less a high or luxury one.