"sounds like universal healthcare for any resident"
Dispite what the liberals will try to tell you, we have universal healthcare everywhere in this country. All you have to do is go to an emergency room and they are obligated to treat you, or at least see you as a patient.
I have worked as a paramedic for more than 20 years in Las Vegas Nevada (with some time spent in Ohio, West Virginia, Pennsylvania, and Southern California. I have worked for private ambulance compainies (7+ years), volunteer ambulance companies (briefly), as well as a municipal fire department (13+ years). I have personally taken thousands of "bums"/"homeless"/"urban nomads".......... to hospital emergency rooms. Sometimes they actually wanted healthcare, but the vast majority of the time they simply wanted to get inside, out of the weather and get a free meal or more commonly they passed out drunk in the street and someone from the public thought they were doing them a big favor by calling an ambulance on them. Another very common senario is the property owner will call an ambulance on a bum so that the bum is evicted from their property. No matter the specific senario, they are taken promptly to a hospital emergency room where they are treated without question and without them paying for any of it.
FWIW in that 20+ years I have very seldom worked a whole shift without running a call on at least one homeless person. The "part of town" I happened to be working in that day didn't matter.
I see no reason at all why "bums" from anywhere else would flock to San Francisco because of health care: they get that anywhere in the country. I wish they would all just go there for the nice weather.