Hi Oskar hope you are doing well.
I normally conmute 6 weeks to San Francisco.
Te extended stay works very well if you can afford an economy card you can stay in a xtended stay hotel (www.xtendedstay.com) for 15 hundred a month this is less than 50 a day and you have kitchen I normally do this way and works fine with me...
another resourde is hostels.com there is a hostel downtown in Sf great place for a traveler at only $15 a night.
hope taht help... and keep me posted on what are you doing now,
Need closed.