2nd part is right, first is wrong tbh. The engines in the Legend can munch head gaskets, the boxes are a little too delicate and there is a whole world of electrics to go wrong that not enough people know enough about.
The nature of the the ***** prestige market is this: It costs little to buy, it CAN cost little to run but don't bet on it. My 728 cost 1200 to buy and just over half that again in 14 months - suspension, alternator, battery... The 528 hasn't cost a penny in 8 months. Any car can cost big money to fix and look at it this way: Your cheapo ***** presitge dies a horrible death, you flog it for £500 on ebay to a breaker and buy another. Your nice, expensive car goes badly wrong, you've gotta fix it.
If you want a proper granddad car, buy on history, quality and keep a wad aside to fix it when it goes wrong.
Edit/ I do realise that the legend will probably be cheaper to run than a 7 series, but that's like saying a coke habit is cheaper than a crack habit