Taylor Swift On the Hunt Again -- For Mansions

For everyone who thought Taylor Swift was a little psycho for allegedly buying a house in Hyannis Port, MA to be next door to her BF ... well it may be she's just a smart real estate investor, because she's done it again in a WAY more exclusive neighborhood.

Real estate sources tell TMZ ... Taylor has been looking at one of the most famous properties in Rhode Island -- the Harkness House -- an 11k-plus-square-foot mansion that sits on 5.23 acres of prime real estate.

To give you an idea of how rich she is ... the asking price is North of $20 mil.

Taylor brought her family and real estate agent to the property on Monday and nosed around for a while. We're told she spent a lot of time there and really dug it.