If you are fortunate, hard working, intelligent, very good at research and a bit more fortunate, it might be possible to finish work for your PhD in two years. It is however quite unlikely that the university would let you finish - it gives a bad impression if universities give out PhDs for only two years work (and they'll be keen to get a third year of fees from you). Also no matter how well you've done or hard you've worked you'll still only have 2 years research experience instead of three. In practice therefore you would spend the third year pretending to still be working and handing your already finished thesis to your supervisor 1 chapter at a time (as if they're only just completed). In the mean time you could have a cheap off season self catering holiday in Malta for 6 months or get some work to pay off your debts.
In reality most students do not submit their thesis within three years, let alone two. By all means make it an aim, but don't plan your finances around it.