He and a 12-year-old deny carrying out a serious sexual assault at the flat in Anfield in September last year.
The boy told the jury at Liverpool Crown Court that he and a friend had been invited into the woman's flat.
The 14-year-old, who was 13 at the time, said the woman began touching his leg while drinking cider.
When she asked for money for more cider, the boy, who has learning difficulties, asked for sex in return and he told the jury she consented.
He told the court that when he refused to give her money she spat at him and he urinated on her, an act he confessed made him feel "ashamed" and "embarrassed."
The prosecution claim the two defendants, acting together, subjected the woman to a humiliating sexual assault.
The younger boy denies of aiding and abetting rape and two sexual assaults. The 14-year-old denies rape and three sexual assaults.
The trial continues.
A 14-year-old boy accused of raping a vulnerable woman in her home has told a jury she consented to sex in return for money.