Almost everybody has a mortgage, and the people who are Trump's likely targets probably have expensive homes and maybe second homes or other real property as well. If you misstate your financial circumstances - income, assets, debts, etc., when applying for a mortgage, you can be charged with mortgage fraud if you did it intentionally for the purpose of obtaining a mortgage you wouldn't qualify for otherwise. But it's really easy to go sifting through the financial records of politicians and other public figures because a lot of that information is readily available, and make a claim that the person's assets weren't as valuable as they'd claimed, or they didn't actually make that much money, and now the burden is on the accused person to prove either that the records are accurate or that there was an inadvertent error, not an intent to misstate the numbers. It's just harassment, obviously. And didn't Trump do exactly the same thing? He overstated his assets to get loans and understated them for insurance purposes. Every accusation is a confession with this crowd.