Taylor Swift's properties are a magnet for strange men with unrealistic and unnerving expectations ... and the latest one was nabbed early Wednesday morning outside her Rhode Island home.

Law enforcement sources tell TMZ ... a man was busted trying to enter the gate of Swift's mansion in Westerly, RI. We're told he did not have any weapons on him, and cops took him to a hospital for mental evaluation.

Another source tells us the suspect claimed he had talked on the phone with Taylor and he told them he was there to marry her.

We're told he is NOT a repeat offender -- as we've reported, Taylor's had several unwanted visitors show up at her waterfront home. A white pickup truck with odd scrawling, on the inside and out, was towed from in front of the Swift home.

These photos show some of the disturbing hand-drawn images, and it appears the man was sleeping in the backseat.

No charges have been filed, and Taylor was not home during the incident.

Just last month, a 32-year-old man was arrested near this home after acting suspicious and carrying around a backpack with a metal bat, gloves, lock picks and a crowbar inside. He allegedly told cops he was there to "catch up with Taylor Swift."

Of course, she also dealt with a scary stalker situation last year and had another intruder at her Beverly Hills property.

These dudes really need to calm down.