One way you can make a little money on the side is by reselling your finds from garage sales that you deem interesting or valuable. If you've really got an eye for antiques or unique items, this can be a very profitable way to spend a summer! Here are some tips to get you started on this potential for a small business.
Shop for things you know will upsell. While it's great if you can at least get your money back on items you purchase secondhand, the effort you put into it won't be worth it unless you can get some extra money. Shop garage sales for items people are eager to get rid of, which you know will bring in more profit elsewhere -- popular books or games, DVD titles, jewelry, and antiques. Think carefully about how much you might be able to sell the item back for, and make sure the profit margin is worth it.
Get information on an item from the host. This is the paragraph you see on a site like eBay or craigslist, where a detailed description of the item convinces you that it's legitimate and worth it to buy. Instead of needing to write this for yourself, ask the host about more unique or rare items, and use what they tell you to flesh out your item description. It'll also make it easier for you to find a target audience to advertise to!
Make attractive listings, including pictures if possible. Log on to a site like eBay or craigslist, whichever you deem better for the types of items you're selling, and start creating listings. Fill them out with as many details as you possibly can, from the size to the weight to the history. If you can, take pictures of the items so people can get a better idea of what they're buying.
Just keep in mind that if you continue to do this on a regular basis, it essentially turns into a side business, making it taxable. It may turn out to be a wise decision, since you can write off anything you use (and keep a receipt for) to run the business -- internet connection, gas to go find the objects, even a new office chair or desk! But you'll need to keep solid records if you decide to go this route, so start saving paperwork even if you're undecided to begin with.
Since much of your merchandise will come from garage sales, GarageSaleCow.com will be a handy tool for your new pastime!