Living in San Francisco is expensive. There was news about Google engineer living on Google campus, so he can save money on rental and save time on parking at least 2 hours in the traffic jam. You can't say he is stupid. In some ways, he is quite smart as a bachelor.
If you are looking price under 100,000 USD to purchase a 1-bedroom unit in San Francisco. You could consider the mobile home. Even you will see it on the market, it is still very rare.
What's an RV or Mobile home?
Mobile home or RV is the home on the wheel. Similar to Mobile home are Modular Homes and Manufactured Homes, the biggest difference is they don't have a wheel, so you need to move the home by truck. It is another world, surprisingly they are still existing in the USA. It gives you the basic need for living room, kitchen, bathroom, and bedroom. You could buy a new Mobile home for 30-40,000 USD.
If you decide to live longer in the center of San Francisco, you would need to purchase the ownership of the location. If you decide to purchase within the RV park, which they will give you electricity and water, then you need to apply with a possible application fee, which you're not sure if you will be approved. For such location, renting a unit is 1,500 USD per month, having a used mobile home needed renovation in a good location is 80-90,000 USD. Comparing to the single family unit, on the east bay of San Francisco is 400,000 USD to buy.
If you have any question, please feel free to leave your comment, or discuss with us.