You've gotten all these different prices and different opinions because
the painters are all working their own agenda; some are pricing for a good
job, some for a not-so-good job. Write your own specs and have each
painter give you a price. Note how some of them will whine about you "not
needing to do" certain steps you specify. As others have noted, prep is
key; so some of the following steps may or may not be applicable. Here are
the basic steps for a good job:

1. Pressure wash the house.
2. Sand down to bare wood.
3. Replace any cracked or broken boards.
4. Tighten up all the nails.
5. Set the nails below the surface with a nail set.
6. Prime the entire house.
7. Putty/spackle, and caulk all holes and cracks, including all the siding gaps.
8. Hand sand.
9. Prime again.
10. Hand sand.
11. Two finish coats, oil or latex, your pick.

--
Jedd Haas - Artist
http://www.gallerytungsten.com
http://www.epsno.com