A cheap beater guitar will recoup next to nothing from the outlay cost if you sell it on. A second-hand instrument will recoup most of the outlay, since it has already depreciated.

If you cannot find a used instrument, you may be able to do a deal with a local tutor. Since they know why you are buying the new instrument and for how long you will be playing it, they may be prepared to pay over the normal odds (but still a discount on the new price) to take it off your hands as a loaner to pupils.