Tenant signed lease agreement for 1 year, paid first and last months rent and changed the mind because there is no closets

First what do you mean by "cancelled"

And sorry they can't just change their minds, once the lease is signed and money paid, the lease is valid, And they may only get out of the lease by terms in the lease.

1. did they not inspect the house or apartment prior to renting it ?

But basically you just tell them sorry no, they can not just not rent, and you will hold them liable for the lease, and if they move out ( or don't move in) they will have to pay rent till you find a new renter.

As Chuck noted, if the Lease was validly executed, they are responsible for it. Tell them you will start immediately trying to find a new tenant, but until you do, they are responsible for the rental. In addition you may be able to hold them responsible for your costs in obtaining a new tenant.

Do this in writing.