This was brought up a couple of years ago. The consensus then was that it was cheat.
Portsmouth may have done something similar, but that was due to the circumstance that they were going bankrupt.
If a club did this normally for purely financial gain, when it was unnecessary for them to do so, the media would be all over them, the manager would most likely be forced to resign, the club may even be taken to court for purchasing goods under false pretences.
With this in mind, I must say I consider it cheating, just because the game lets you do it doesnt mean you should... remember the corner cheat of FM2010 or the "Diablo Tactic" of CM03/04?...
Yet I must admit the "Diablo Tactic" was funny when your AMC scored over 100 goals a season.