Mr Justice Henriques said Ryan had a history of borrowing cash from people with "no intention" of ever repaying it.
He said Ryan targeted Ms Lee as a potential source of money, adding: "You literally bled her dry."
The judge said: "You suffer from the toxic combination of being work-shy and grossly extravagant."
He said the defendant had never had a "job of any substance" but still drove around in a BMW or a Mercedes and wore "expensive clothes".
"Your extravagance knew no bounds," the judge said.
"As your friend said, you bought only the best, and then you met Diana Lee."
The judge said it was not possible to know what lies Ryan had told Ms Lee to separate her from her money but he said he agreed with the prosecution's claim that he must have "tempted" her into some kind of bogus business venture.
Mr Justice Henriques said Ryan decided to kill Ms Lee when she started asking questions about what he had done with her money.
He said: "You killed Diana Lee to prevent your spectacular fraud upon her coming to light."
The judge rejected the defence's claim that the killing was spontaneous but added: "I accept, however, that if you could have strung her along indefinitely then you would have done so."
He said it was Ryan's intention to destroy all evidence by mutilating her body and getting rid of his DNA and then setting fire to Ms Lee and her house.
He said Ryan believed he had "planned the perfect murder" but a lack of oxygen in the garage prevented the fire from spreading and destroying all the evidence.
"You mutilated Diana Lee's body in a shocking and very disturbing way - something which will cause extreme distress to all who loved her and all who knew her," Mr Justice Henriques told Ryan.
He said the murder was premeditated and said Ryan had taken the life of a "much admired woman" whom he described as "kind and sensitive", "hard-working", "happy" and "positive".