A1181 refers to a family of white (and black) thermoplastic case MacBooks built from 2006 through October 2009. Outwardly, they all look pretty much alike.
Battery condition is not mentioned. Have the user boot up the computer and show you , About This Mac, More Info..., Hardware, Power.
If the battery condition says 'Replace Battery', that's exactly what you'll need to do.
The battery of these models is designed to be removable, and can easily be replaced by the user. Replacement batteries directly from Apple cost $129. There are lower-cost battery suppliers, and user experience with lower cost batteries ranges from spectacular to rip-off. Original equipment batteries were designed to achieve at least 300 charge/discharge cycles and/or about 3 years of useful life.
Before you make a purchase decision, get the system serial number so you can look up the exact model details here:
http://www.everymac.com/
Be certain that 'included software' includes the Apple-logo system CD/DVD discs, which should include an OS X system discs, likely OS X 10.5 'Leopard' or OS X 10.6 'Snow Leopard'. If those discs are not included, you can purchase them directly from Apple, but replacement discs are not free. The MS-Office disc should also be included, if the owner is transferring that license to you.
The images on the Craigslist page show that the topcase (combined keyboard, trackpad, and palm rest assembly) has the 'chipping' or 'splitting' on the edge of the right-hand palm rest area so typical of that generation.
If it IS the mid-2009 model, it CAN run OS X 10.9 Mavericks, currently available as a free download from the Mac App Store.
At best, you're getting a gently-used 5-year-old MacBook with many useful days of productivity remaining.
At worst, you'll need to replace the battery soon, and the hard drive sooner or later, either because it fails or because you've run out of available space.
Check other sources online. Purchasers of used Macs who purchase them for resale, like the one linked below, who offers about $75 for one in perfect condition.
http://www.sellyourmac.com