HalfGerman

Guy on Quattroworld has this, hopefully not too far for you:
http://www.tibbettsproperties.com/storage.htm

Don't know anything personally about it , just passing it along.

YellowDieselGolf

There's a service called Park Hound in Australia. A bit like airb&b for cars. Maybe there's an equivalent that covers Boston?

nile13

There are a few parking spot-finding apps, but they are mostly aimed at hourly or daily parking, not long term.

HalfGerman, thanks! It's a bit far, 2 hours' drive. And they seem to charge $15 per foot, which, I assume, would be $200+ per month, if I understood correctly.