One is to keep interior walls permeable (online references) and one is to try to seal them (experienced construction guy). 

SF offers almost a complete lack of urban sprawl combined with very liberal city politics (a.k.a. stiff construction regulations) located in the hub of the growing tech industry means a strong investors market, if you can scrape up enough cash for the buy in.

I am a project manager for exterior construction so I don't deal with interior jobs, but you should be able to know at least 80-90% of what needs to be done and what the real cost is through estimating the project.

I know were we are going to get frustrated is in all our new construction homes we are selling. its already bad enough in some markets..

I want to make sure I understand what's required before using real dollars for deals.I used to build some spec homes with my brother, so I understand construction, dealing with contractors, etc... 

I also have partnered with people in the construction and development business.  

Here is how to do it in any market 1) block must I repeat must be desirable for the area (one or two vacant buildings and no bad elements)2) good property management (treat your tenants like hotel guests)3) buy well high yield for higher risk4) solid construction with lots of upgrades keeps tenants long term.

Not to mention how closely tied they are to the construction business. 

My dad is retired and was a property and construction manager so that's another option but he tends to disappear without warning.  

https://www.biggerpockets.com/forums/12/topics/232...I have a background in interior design & certificate in Building Construction.