We have tulip trees here in zone 5 and they flourish easily, so I see no reason they wouldn't be able to live in zone 4. You should be aware that they have a very extensive invasive root system. Be aware that if your tree has the status of heritage tree and receives protection so that it cannot be taken down in the future that it may affect the value of your property depending on where it is located in relation to structures or to a desirable garden area. Some people may not be interested in purchasing the property knowing the tree cannot be taken down if they want to. I know I would not buy a property as such. First thing I did when we bought our home was cut down most of the large trees. I did not want them hanging over our buildings, did not want the pollen in the air, around my home and wanted to make room for a koi pond and vegetable and daylily gardens. Tulip trees grow easily from seed and spread all over the place around here. They are probably the hybrid kinds? I don't know, but they borderline on invasive and are not long lived trees as the oakes and other hardwoods.