Looks like there are nonstop philidelphia to SFO flights for about $250/roundtrip. So say he's burning $1,000/month on his commute ($12k/year), an RN in SF makes ~$120,000/year ($75k after taxes), and ~$70,000/year in Philadelphia ($50k after taxes). Based on all that he's making a net of an extra $13,000/year from living half the time in a trailer in San Francisco.
If all those estimates are right, it'll take a lot of years of flying across the country to pay off that last sentence.