Topping the rent charts nationwide, $3500/month for 1-bedroom unit is as real as is obscene. But where did it go wrong for San Francisco and is it really so bad as it looks? The supply side is pretty straightforward: available housing in San Francisco is scarce. Here’s why: Geographic constraints. Bay Area doesn’t have much land available to build out. San Francisco is a 7-by-7 mile city with sprawling problematic,…