It looks like the city of boston shares a lot of their data for public use which could be a good starting point for anyone wanting to take on this project. (Depending on their workflow)

https://data.seattle.gov/browse?category=Land+Base&provenance=official
-Specifically the Cadastral lot data and the street data. should be helpful.
-Heck they even have data for the sidwalks depending on the map's scale
- In general the sheer amount of data available for mapping in this area is a goldmine (speaking as someone who works in an area really behind the times on data sharing)