||I took my sedan from Dallas to San Antonio with 4 adults (me included) I'm sure they weren't Cadillac DeVille comfortable but ok comfortable for hours.
Now talking on price. I will be speaking in cash prices because financing is something? different. If someone is selling a car for 13k most likely they priced it high because they already know someones going to knock it down. So if I was offered 10k I would of course counter back. If I priced it 13k most likely my lowest will be around 11,500 and of course it all depends on what the prices of the car is. If they're typically around 14,500 and I ask 13k I will be pretty firm around the 12,500.
Now with that out the way. I know it was a example but 13k for 04-06 G is too damn much. There are some dealers that charge $500-800 dollars per car for using they're license at a wholesale auction to buy. They give you access and you risk the rest. I've been lucky to get really good prices on G35's the cheapest I've bought I think was in 2015 and it was a 04 with 116k miles for $2,000 plus buyers fee (auction fee) so it was around 2,250. It had heating problems, at the end it was a radiator, front bumper, oil change, 4 gentley used tires. 1 upholstered seat and pad/rotor change total cost of $900 ish. Sold it for 6,500 cash I'll see the car running around today kicking ass down the streets.
Long story short try to find a dealer who would give you access. If not a 06 with 120k miles in really good shape would be no higher than 6,000 in retail/private party. If you read this far sorry for the long conversation.