A quarter-million-miles vehicle for $6K? Sounds high to me, knowing little else about it.
I'd want to see the service/repair history. I'd want to know the specific schedule of changing all fluids (engine oil, transm, transfer case, rear diff, coolant). I'd want a compression test and perhaps leak-down test, at that mileage. Would want to understand the condition of the mounts and bushings, since 250Kmi can put them through their paces. I'd question the suspension. All of that, particularly if not having documentary proof of services performed. On a vehicle with this many miles, If I could get it I'd love to see an oil analysis of the engine oil and transm fluid. Suspension, as well, which at 250K ought to have had the shocks/parts swapped long since.
Perhaps nothing's wrong with the car, and perhaps maintenance history has been stellar; perhaps not. But, that's me ... and I'm fairly conservative when it comes to well-used, high-mileage vehicles.
Still, it's a CX-5. Overall, a solid vehicle. Assuming the above has been well taken care of.