How can I get $400-$500 within a little over a month?

Well, all my ideas are "online stuff", so if that is a no go, don't bother to read any further. Also, you'd need some help from your parents to set accounts up for these ideas.

Are you good at writing? If so, you could write articles and blog posts for website owners for money. A well-written, 400 word +, optimized article will bring you about $5. It may take a little practice to write an "optimized" style - including specified keywords early on in your articles, including a couple "long tail" keywords in the article, etc. but not that big of a deal after a little practice.

I think Associated Content at least used to pay for articles, there are also plenty of writing gigs on freelance websites such as ScriptLance, Freelancer, Getacoder, etc.

You could also try fiverr.com. Go there and look at some of the gigs, and copy one that you think you could do.

Maybe give eBay a shot. If you have some stuff that is worth something that you do not want anymore, listed on eBay. Ask your buddies if they have anything that they want to sell, and offer to sell it for them on eBay for a cut.

You could even try "eBay arbitrage", where you buy something off of eBay and then resell it there for a profit. Some sellers do not include important keywords in the title, give a poor description, poor pictures (or none at all), etc. All this stuff can scare potential buyers away, decreasing the competition and probably the final price.

You could possibly buy the items and make a much better listing, and possibly profit.

Sellers may misspell the main keywords in the title as well, meaning most potential buyers will never find them. You could try a misspelling search using a site like Typojoe.com to hopefully find some of these items and possibly get some great deals.

You could also use a site like Ebuyersedge.com to set up saved eBay searches. You'd get an e-mail whenever a matching item is newly listed. Especially good for "Buy It Now"s that are priced right. You could set up your saved searches and then from there all you would be doing would be checking e-mails when you get them sent to you and looking at the items, so there should not be a whole lot of time involved in setting up your "system". You'd have the jump on other potential buyers.

Or, if you find something you want listed an auction format, use a sniping service such as Hidbid.com to place your bid for you. It'll bid in the last few seconds, helping you to save money and avoid shill bidding.

You could also try your local thrift stores, Goodwill, auctions, yard sales, Craigslist, etc. to source products. Having a smart phone with internet access would be a big help with this. You could check prices of completed listings immediately, deciding if there's enough room for profit for you to buy a particular item. It seems there should always be room for smaller sellers on eBay for used items.

Or, rather than selling a physical product, maybe try offering a service on eBay. Maybe writing articles, creating graphics, whatever it is that you would be good enough at to charge for.