Dust -what solutions are there?

I am looking to buy an entry level DSLR. Whilst the Olympus E-300
reviews have not given me much motivation to buy the camera, it has
raised a point that I had not considered before - the question of dust.
(For those who haven't read the reviews, a selling point of the E-300
is a special feature to shake the sensor on startup to remove dust).

So my questions a

1) How often do you need to clean the dust from a DSLR, assuming using
two lenses, and swapping between them regluarly?
2) Is this a home or professional job?
3) If you clean it yourself what equipment do you need? If its a
professional job, what might you pay?

Thanks for your thoughts,
Tim