Am I free to walk away from this deal?

How long is "a few weeks?" You haven't signed the lease, so you can definitely walk away without penalty. Just inform the landlord that you've changed your mind. Whether or not you get the $100 deposit back depends on what your anticipated move-in date would have been. If it was close to a month away, then you would likely be entitled to that money back. But if you would have moved in within the next week or two, the the landlord is losing out on a month's rent if they're unable to find another tenant, and they may be able to keep your money. Regulations vary depending on where you live. Your town council office can tell you for sure.