When purchasing a condo, some of the lender requirements have become more stringent.

1. They are looking into the number of rental units vs. owner occupied units in a building.  If the condo has over 30% rental units, you may have a problem getting financing.
2. Also check for HOA delinquencies. Some of the lenders have been focusing on the number of tenants not paying their HOA fees.  The less people in a building paying their HOA fees the less likely you are to get financing for that condo you are looking. 

For more information about condos in San Francisco feel free to contact me.