I'd be weary of a G2 that is being sold for under $5k. That being said, Legends are "Honda reliable". Maintenance costs are a little higher than the average car as parts can sometimes be expensive, but overall, outside of regular maintenance items, few things break.
Known, and somewhat common issues are a cracked radiator, faulty door lock actuator, broken transmission mount... err.... that's all I can think of right now. These are basically change-once-in-a-long-time type items.
Other than that, the largest maintenance item is the timing belt/water pump service at 90k.
Legends, well taken care off, can easily go 300,000 miles, and have been known to go much longer than that.