Quiet,
Good questions there.
Domain buying and selling is like anything. You try and buy low or at a good price and sell high.
We bought tons of domains in the old days and if the price is right, we sell 2-3 a year or so. Unless it's a super generic word or has good typins / traffic, always be careful and study before buying.
Kinda like the stock market, speculation you know. Like I got oilforsale.com a few years back, not that good of a name at all, but you know everytime there is a gas crunch or prices are going up alot, I get 3-6 emails about selling that domain
Lots of other examples you know.
With a bit of a shitty economy right now, it's a good time to buy some domains and put them away for awhile.