If a second space is needed, parking in Cambridge is priceless - as are single families. If all else is equal, and the property you want has 2 spaces, it would be worth it to pay more than if it had one...even if you don't need the space yourself. How much more? definitely would depend on the price/location of the home, but I'd say between 10 and 20K . Each property must be evaluated independly, and with the help of an experienced professional.
If you are not currently under contract with a Buyer's Agent - you should be. A Buyer's Agent will do an analysis of the property for you to help you determine the "right" price. If you are looking for a Buyer's Agent to work with, let me know and we can talk and see if we would make a good Home Buying Team.
I strive to provide a painless and pleasureable Real Estate experience for my clients.