$5,000 for a garage however in some neighborhoods there is money avaliable through a private non-profit organization for doing improvements like either building a new garage or
fixing the old tuck under. For me, if everything else fits, lack of a garage should not be a deal breaker for you it's a realitively easy fix. There are also loans specific to making home
It really depends on the buyers needs when re-selling the house. With that said most buyers place a medium to high importance on having that space to park their vehicles or for the additional storage. I have had estimates done before for a two car datached garage for $20,000 to $30,000 given materials. I would reccomend having a contractor come estimate that cost for you.
I am not familar with the nieghboorhood or house but will say it would be a wise investment for future re-sale.