Winter-weary Americans seeking a faraway getaway in the tropics can buy a place right on U.S. soil.

Puerto Rico, unlike most other tropical locales, is a U.S. territory, so the same mortgage-financing rules apply there as in the 50 states. Jumbo loans start at $417,001 in Puerto Rico, like most U.S. locations. In two other territories, Guam and the U.S. Virgin Islands, jumbos start at $625,501, the same as other high-cost areas, such as New York, San Francisco and Hawaii.

Borrowers...