A a simple question that requires a particularly unsimple answer. there are of course some hosting plans that are extremely cheap, places like Hostgator and Godaddy offer US based shared hosting for literally pennies.
However, it is my experience that there is no such thing as cheap hosting, those type of shared accounts are probably fine if you want to throw up an affiliate site or 2 and hope for the best.
I have a business I actually care about, therefore now stay well away from those accounts (I have used them in the past). Personally I am in the UK and use a company called Enterprising Internet (.com) who offer hosting accounts from pennies that match the features of the bigger hosts but with personal service, excellent backup and security facilities and best of all the company is run by Internet marketers and they are always willing to discuss tactics and offer advice. All for the same sort of cost and hosted on a range of servers with load balancing etc etc.
Hosting plans are wide and varied but we personally use a Linux based plan just for ease of use and the ability to 'plug in' so many technologies and CPanel to control the features. Really it would depend on your needs, some people have a single shared hosting account with tons of sites hosted in that one place, while we prefer to have several shared hosting accounts in addition to ur dedicated server for the main business. Others use reseller accounts, however this is really no different than having multiple sites in one account.
Basically if you have particular needs you should look at something a bit more bespoke, however if you are throwing together some wordpress and affiliate sites then just about any basic linux package would do. If you want to use Enterprising internet you should let them know when contacting them that you were referred by Jack Pride, they work on a referral basis and are usually cheaper than the large hosts for similar but better packages. - to contact them it is hosting @ enterprisinginternet.com.