Make sure machine is unplugged. Open or remove the cover. Loosen the vertical guide bar holding the blade guides and see if it slides up and down without binding.
Besides the tires aquinob mentions, check the bearing behind the blade for smooth rotation and have a look at the other blade bearing under the table, plus the condition of the guide blocks. Were the blocks properly adjusted by the prior owner? They should be very close to the blade but behind the blade teeth. Look for any burrs, scoring or damage of the components under the table that can be used to negotiate the price. Look at the condition of the drive belt, belt alignment and pulleys. Take note of the currently set blade tension by deflecting the blade. Pull the blade and spin the top wheel to check for the bearing condition. Reinstall the blade, set the tension, plug in and run the saw. Look for vibration, drive belt operation, and any wobble of the pulleys. Put a coin flat on the table away from the blade to see if it moves around while the saw is running.
Any extra blades included?
Cast iron table is a plus.
Included task light is a plus.
Enclosed base is a plus.
Sheet metal covers instead of cast can be a minor negotiation point.
I'd offer $375 and settle on $400. Your location (not stated) will affect pricing. May want to watch a video of bandsaw operation/adjustment.