If you have not chosen an architect, I would interview at least 3 and get their ideas. They should be able to give you an idea of what approach they recommend and some budget pricing.
Keller Williams Realty
I do not think a Realtor is qualified to answer that question. Need a geological report on the land and building contractor for professional answer to question.Good Luck!
Gail Mercedes Cole
EXP Realty Marina del Rey