Quote from @Ori Skloot:
IMHO, the big wrench in your plans is your estimated cost of construction. I'm a general contractor and have a good sense of building costs in the Bay Area. $400k for 1200 square foot new build that requires sprinklers is not realistic. I would budget a minimum of $400/sqft and more likely $450+/sqft. For your underwriting I would be conservative and make sure that the numbers work even with the top end of construction costs.
Thanks for your alternative viewpoint Ori. I think your more realistic cost per sqft of $450 is my worst case scenario. For 2400 sq ft that puts me at $1,080,000. I believe the biggest costs will be the utilities so I will definitely make sure I understand if my existing water meter size, electrical service, sewer lines and gas is adequate or if I will need to dig and upgrade which will cost big $$$.
The 3 unit building I live in right now is 4500 sq feet and is a 100 year old mansion. I bought the house 20 years ago with fire damage and I completely gutted it down to the studs and did a very high end remodel and added sprinklers. I remember at the time I was told it would cost me $500/sq ft to do a high end remodel. I did a lot of the design work myself designing the kitchens and picking out and buying all the materials myself. There's so many ways to save on costs like using those $100 per slab granite counter top places you find in the industrial areas of the bay instead of walking into a showroom and buying overpriced granite. I was able to do the whole job for $800k instead of the $2MM everyone kept telling me. If I just hired a GC to do the whole thing I might have paid double. I know things have changed in the past 20 years so maybe there's not as many areas to save. I did get all my grey hairs from that renovation project so while I did save a lot of money it was at a cost. I am not looking forward to dealing with all this again but life is hard whether you are working in a cubicle or dealing with construction projects so we have to pick our hard.