Some of those used to be assumable by anyone.
The problem is that most will be paid down significantly and you will need to make up the value difference.
Assumable mortgages usually only exist in books and TV real estate courses, today.
I would contact a local real estate professional to help with this answer and to save time and money.
(I'm on the Cape, but I can help you choose a local pro if you want help doing so.)
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Your best bet might be doing gauge a realtor they can just help you find a property that you're looking for the right price