Well it's after an '87 model because it has the flared seat. 85 and 86 had a straight seat like the blaster.
I would probably go look at it in person before I made any decision about it. It looks kind of rough in the photo but that's not a real good indication of how someone kept up with the thing. You need to see if the brakepads are down to metal backer, if the shocks are leaking oil anywhere, if any bearings have play in them, if anything is bent out of whack, and if the engine/transmission looks like it's ever been into.
If he ran it out of fuel on a hard pass he might have gouged the piston to the cylinder but the rest of the bike isn't in bad shape (except for the seat cover) it's worth $300 then. If everything on it is wore out and about to fell off, it's not worth $300 because not only do you have an unknown problem in the motor which could be simple or very costly, then you have other costs involved with putting it back together.