how much does the average 1200 sqaure foot house cost In San Jose, California?

You can google that for an answer. 

A quick search on realtor.com

Homes that size are $700,000 and up. Many are over $900,000. 

https://www.realtor.com/realestateandhomes-detail/...

Take a look at Zillow.com.  You can get an average house for maybe $600,000 - 700,000.  If you don't care too much about neighborhood.

I grew up in San Jose.  The house my parents bought for $17,500 in 1961 sold for $700,000 five or six years ago.

Average 1200 square foot house?  That is barely the average size of an apartment.

If you want home prices, use zillow or a similar sevice.

the greatest cost is you live in California...