Really depends on the shape they keep it in. I initially thought you meant an Apple store on/near military base, but that may not be the case. I'd inspect it on the outside for signs of damage and then you have a warranty so I wouldn't worry. They will probably wipe the OS before purchase, but if not then I'd reinstall the OS at home and enjoy the machine.
If it's not an actual Apple store, you may also want to check to see if it's a 2015 or 2017 model. It's less of a steal if it's a 2015 model as you can get a certified refurb for about that price.