Rent vs Purchase Used (selling after trip): 4-6 month trip

If it was me;
I would buy used and pay cash. Use how ever long I wish and then sell. If buying a used unit and selling in 6 months depreciation is virtually nonexistent.

If you buy at a good price you may even be able to resell at a profit. I have bought and sold several units that I never used for a single night, just bought low and sold high.

On the other hand after this trip you may wish to keep the unit, you cannot do that with a rental.