partner backed out on agreement leaving me with a 2 yr lease on store front, what can I do?

A party to an agreement can't just "back out" because he wants to.  If you had an agreement (in most cases it can be oral) you can sue to enforce it and/or to collect damages for its breach.  Also, in some cases, you may be able to collect for damages you suffered due to your reasonable and detrimental reliance on your "partner's" representation (i.e. you entered into a lease based on your reliance n his/her promise to go into business) even if you can't prove an enforceable agreement.