Well, to purchace is easy, u can do it at godaddy.com they are very cheap and reliable... you get your password which will controll the domain, i.e. if you need to change the host service you just log in with your username and details and change the DSN.
Selling... you offer it for sale (AFTER you have registered and it's yours), and when someone buys it from you, you just give him your username and password.
Good luck!
If you think to resell domain names
without having a reseller account
I want you recommend ENOM
becouse access.enom.com
is best domain name control panel,
but for regular clients they are extra expensive
30$ per year.
5 dedicated servers in USA & Europe - 200.0Mbps speed. 99.9% SLA Uptime. 5 years on the webhosting market ! Mirror Hosting. ULTRAFASTHOST - with the price of the quality !
Over at the online tools (free) center at WebHelperNow.com, they have a domain look-up form that shows domains for sale (if someone owns them) and an offer taking/selling system through a company called SEDO. Go to: http://webhelpernow.com/wordpress/?page_id=62
Enter (top of that page) this domain name: CoffeeNutHut.com -- if you want to see one I know of that is for sale and see how their system works. The system also returns available domains that you can purchase right away.