Will you be able to see/play the guitar before you buy it? Being a local guitar, hopefully so. This is particularly important if you don't know the seller. All kinds of claims can be made about guitars being "little used" that turn out to have had the living **** beat out of them. And photos can be misleading.
As far as what to look at--all the usual things. Condition of the neck is always paramount to me (straightness, freedom from twist, fret condition, etc.). Electronics should also be checked out, as they are often a weak spot on less expensive guitars. Confirm everything is fully functional and free from scratchiness, signal drop-outs, etc. Set-up issues are less important, because they can be adjusted, as long as there are no fundamental physical defects behind them. Check out the tuners--does the guitar tune & hold tune well? Are there missing parts, including less obvious ones like trem block springs? And if it's a MIM Strat, that should, of course, be indicated on the headstock decal, along with a serial number that corresponds to the claimed point of origin and date of manufacture.