However - I waned on the project because of the amount of cap-ex and maintenance required.

This is a major renovation that would include interior and exterior projects.

At some point a surge of vacancy seems logical as more of the displaced homeowners resettle into their homes and the new inventory keeps getting added.The wildcard of it all is, how much new demand that will fill the vacancies at rates based on projected population growth. 

A great place to educate yourself is the SFMTA website where all the projects they are currently working on are listed.https://www.sfmta.com/projectsThe other way you could speculate is by following sheer density, such as Mission Bay or Potrero Hill where there are a lot of new developments going up - almost endlessly.

But I also was stood up a number of times, or had contractors come take a look and tell me the project was too big.  

You won't know TRUE cost/SF until the project is built.In our market, we use cost/SF as a back-end development metric. 

This owner is checked out and the broker let us know the projected gross rents for this year will be $125k.

I assume that although you took on a pretty big project in a new area making you essentially a 'newbie' - your previous BRRRR experience definitely must have contributed to the success on this project. 

Once it’s fixed up you can refinance it off of the projected ARV.

I'm reading about it but I thought I'd ask people out there doing it. 3) I'm willing to work on a project with someone to learn more.