Hi--Good questions. I also relocated from NY (but about 12 years ago), and I think the transition is easier if you select a neighborhood that offers the amenities you're used to having in NY. These would include a walkable location with proximity to public transportation and restaurants, bars, etc.
Your timeframe for living in your unit is reasonable, even more so if you are planning to potentially renting out the property once you leave. You are looking in a very popular price range; over the past three weeks, I have been contacted on a regular basis by Trulia visitors seeking the same type of home.
There are 75 1BR+ units on the market right now for up to $500,000. Some of these are senior housing, so that narrows down the field a bit. :) The Palms is a good South of Market location, but it has been hit hard by short sales & foreclosures, and I am a little hesitant to recommend it as a good investment. Opera Plaza is not bad, but the crowd is not quite young & hip, and the HOA dues are high. (My office is in one of the commercial spaces in Opera Plaza.)
Without knowing where you will be commuting, etc., I recommend focusing on the South of Market area. You'll get the most space for your money, but just watch the HOA dues amounts. Those are usually included in listing information. Also, something like 38 Landers might work for you--this is a 1BR cottage condo in Mission Dolores listed at $469,000. Parking is leased, but HOA dues are $235.
Feel free to message me if you'd like further info, and check out my blog, which has good info for first-time home buyers.