I am not a legal professional, but it is fair to assume it will be much like buying any real property for cash.
Pricing widely varies in Boston. You can find parking for sale listings on MLS or Craig's List. A parking space in Cleveland Circle which will rent for $150 will sell for about 17- 20K. In Back Bay can easily be triple that, about 75K for a garage space.
Look under condos in MLS, and under parking in Craig's list. Feel free to contact me with further questions. Good luck!
Many parking spaces are listed as either condos or land. This, as deeded properties.
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