(Background: I came from grad school in Seattle to SF for my job.)
(a) Freelance work is heavily dependent on contacts. If you don't have contacts then it's a crapshoot. Maybe you'll luck into something, maybe you won't.
(b) For housing, scan http://sfbay.craigslist.org/sfc/sub/ ; $700 is not impossible, but you'll be living in a spare room of someone's house, and even then that's the low end & you should expect compromises. SF housing is much more expensive than Seattle, as in 2x the cost for equivalent space. I don't know where you got the idea that the costs are comparable (are you mistakenly including East Bay or South Bay prices instead of SF city prices only?). $100 for food is doable if you know how to buy cheap food in bulk and cook it yourself. As for "everything else", heat/electric/broadband can easily consume close to $200 if you're living alone. In a share it should be less, but you should ask about utility costs in your housing situation. On that budget, you should not count on spending any money on entertainment. There's some free entertainment to be had if you're scrappy, but expect to get most of your entertainment from walking around the city or riding your bike through the parks.
(c) Summer SF weather is colder than summer Seattle weather. Bring sweaters.
(d) [you skipped (d)]
(e) SF is an expensive place to live. If this is your 2.5 months of adventure before college, then you just have to weigh whether you're willing to pay $3k for that experience. (Not a bad way to spend it actually.) If you're really trying to bootstrap into a sustainable living situation, SF isn't the best place to go with as little savings as you have; there's too much danger of burning through your seed capital before you get revenue-positive ;). I get the sense that for you it's more the former than the latter --- that is, there's not much downside if you fail --- so what the hell, go for it.
(a) Freelance work is heavily dependent on contacts. If you don't have contacts then it's a crapshoot. Maybe you'll luck into something, maybe you won't.
(b) For housing, scan http://sfbay.craigslist.org/sfc/sub/ ; $700 is not impossible, but you'll be living in a spare room of someone's house, and even then that's the low end & you should expect compromises. SF housing is much more expensive than Seattle, as in 2x the cost for equivalent space. I don't know where you got the idea that the costs are comparable (are you mistakenly including East Bay or South Bay prices instead of SF city prices only?). $100 for food is doable if you know how to buy cheap food in bulk and cook it yourself. As for "everything else", heat/electric/broadband can easily consume close to $200 if you're living alone. In a share it should be less, but you should ask about utility costs in your housing situation. On that budget, you should not count on spending any money on entertainment. There's some free entertainment to be had if you're scrappy, but expect to get most of your entertainment from walking around the city or riding your bike through the parks.
(c) Summer SF weather is colder than summer Seattle weather. Bring sweaters.
(d) [you skipped (d)]
(e) SF is an expensive place to live. If this is your 2.5 months of adventure before college, then you just have to weigh whether you're willing to pay $3k for that experience. (Not a bad way to spend it actually.) If you're really trying to bootstrap into a sustainable living situation, SF isn't the best place to go with as little savings as you have; there's too much danger of burning through your seed capital before you get revenue-positive ;). I get the sense that for you it's more the former than the latter --- that is, there's not much downside if you fail --- so what the hell, go for it.