I noticed that when some people sell a website, they say something like "offering free hosting for 30 days" - do they do things like give you access to the ftp server for the website, or do they simply just give you a log-in info for the site and that's it? (im a newb at selling/buying sites )
Most of the time they have a reseller account, vps or dedicated server big enough to hold a several more accounts. You are basically get a true hosting i.e. have all access to ftp etc like any other hosting although they might limit something on your account.
The reason that they'll offer you a month of hosting is that you really don't understand what they are selling... you think that they are selling you a website. (It took probably less than 10 minutes to set up) What they are selling you is the hosting. They can give you the website for free and make money... because typically most people will not move the site to their own hosting platform (they don't have one...) but they will become a new re-occurring income stream for the person who is REALLY selling hosting... Since it wouldn't be unusual for someone to continue hosting for at least a year... if they were "selling" you a website for $xx, a free month of web hosting, and then monthly hosting fees of $5/mo. - what they have at the end of a year is $55 PLUS the $xx for the site. So they could pay you to take the site, and statistically speaking, make money.
My apologies, I don't log on to DP very often. Yes, normally you'll get a cpanel name/password - which allows you to set anything on your hosting, to include FTP passwords... my recommendation - find one good hosting package that allows unlimited websites, and unlimited MySql databases, and unlimited space... you should be able to find one for around 6 or 7 dollars a month (if paid annually), Hostgator, Hostmonster, FastDomain, Bluehost, there's just a few that seem to come to mind. Then if you buy a good website, simply move it to your hosting. The real trick is learning how to develop your own website - with Wordpress it's quite easy. If you have any other questions, feel free to ask - I'll try to check in here a little more often!!