Duplicate content.

How much does it actually affect SEO? Basically I have a bunch of content I'd like to use for quick profit, is there any method to get it high on search engines even though it's duplicate? I could spin it I guess, but it wouldn't make any sense to the reader.

Google aims(isn't always working) to separates duplicate content from the search results.
There is no use in displaying two of the same contents below one another.
You can however with some seo work rank higher than the original content and be the one getting displayed.

You set up a autoblog and run a few feeds for a some weeks.
You also do a of bit of linkbuilding etc. you get the idea.
After a few weeks you gain rank and pr.
You'll see in the google webmaster tool you'll get crawled at least ones a day.
When that happens drop your old feeds and go search for newbie blogs that have feeds and gather about ten.

The original blog doesn't have as much rank as you nor does it get crawled that much.
So you will always outrank the original content.
After the original blog gains more rank you go search for some new feeds.