I hope someone could teach me a few things about those portable electric
planers like the Dewalt DW680K 3-1/4" portable planer.

Are these only for use on stock that's the same width as the blades, or can
it be reliably used to plane down something as big as 12" stock? I need to
plane a 12"x18" 2/4 piece of stock to 3/8" thick and all of the wood stores
in town I've talked to won't do it unless I buy the wood from them and I
already have all the stock I need.

I don't have much money, so I figure I can put it to better use purchasing
a good quality portable planer as opposed to a very cheap 12" planer. Any
advice is appreciated. Thank you.