I agree with Chris, but would just add that the reason you should be looking at how well it heats up does not have to do with what the temperature actually is (which on a functional machine would be adjustable), but just to make sure that you don't have a broken heating element (or two). If the machine can produce steam, that pretty much confirms that the element(s) are ok. Also, the most expensive leak you can have is a leak from the boiler in a place where there is no gasket, usually on a seam somewhere. Tightening down is free, o-rings and gaskets are cheap, but a breach of the boiler skin requires replacement of the boiler or a good friend or family member who is a talented metalworker.
I forget, is this an HX machine or a double boiler? If it is an HX, and there is water level indicator for the boiler (meaning a window where you can see the boiler fill level from the front of the machine), watch that window while shots are pulled to make sure the boiler is not filling at the same time. If it is, the HX is ruptured, and that would be at least as bad as having a leaky boiler.
...which is not to say that it would be a deal killer, given the outrageously good price! But if that is the case you would want to price out a new boiler before making an offer.
Good luck! Assuming no major problems I envy you for this deal.