Buying and M62 with 200K+ with no records is a ticking time bomb, might blow up at any time! They are notorious for problems arround that milage. Almost every other day i see them on Kijiji; 540/740/X5 needs engine! Be very carefull, or just buy a cheap one and save for new motor!
The other good option is to buy a cheap high milage one with good body/interior, and just spend the rest of the $$$ on getting the engine freshened up, no crazy rebuilds, just the basics that cause the most problems. If the proper things are done at the right time, this motor with run forever.