Over the past turbulent decade, through myriad self-inflicted troubles, Hunter Biden has relied on the kindness of friends and family — wives and girlfriends, business partners, his father and, most recently, a Los Angeles lawyer who provided the president’s son a $7 million lifeline.

But now that lawyer, Kevin Morris, who has played many parts in Mr. Biden’s life — legal adviser, confidant, strategist, art patron and friend — has told associates he is running out of liquid assets to make any more loans, deepening a chronic cash crunch that has already left Mr. Biden’s lawyers working for little or no compensation.

With Mr. Biden’s trial on gun charges set to begin on Monday in Delaware, Mr. Morris has said he might need to sell some real estate holdings or other assets if others do not step up to fill the gap, according to people familiar with the situation. He hopes to pressure the president’s advisers into helping find new donors, people close to the situation said.

Financial troubles are nothing new for President Biden’s son, and his current woes are unlikely to prevent him from mounting a sturdy defense. But it adds a layer of stress and uncertainty, and could limit his ability to hire expert witnesses or other specialists in the gun case or in his trial on tax charges in California in September, they said.

Last year, Mr. Biden was charged with lying about his drug use when he bought a .38 handgun in Delaware in 2018 and with illegally possessing the weapon. He was later charged separately with a series of tax offenses related to his failure to file returns for a number of years.

Mr. Morris has lent Mr. Biden money to cover an array of expenses he incurred in recent years, including his multimillion-dollar back taxes bill and legal expenses stemming from the government’s long-running investigation. Mr. Morris has also helped Mr. Biden on other expenses, including rent on expensive houses in Malibu and payments for a luxury car.