Do I have a valid Florida lease?

This lease is valid if the signor of the lease has authority to sign the lease on behalf of the owner. You can ask the owner to submit to you in writing that the father had authority. If the owner says the father had authority, then you have a lease. If the owner says the father did not have authority you may claim that the father had authority if the owner had knowledge of the lease, allowed you to move in, and did nothing to intercede. Also, very important is whether the owner is excepting rent payments. There are other variables as well.

If for some reason you do not have a valid written lease, if the owner is accepting the rent payments and has not objected to your possession of the property, then you would have a valid oral lease of unspecified term. If rent is paid monthly then you probably have a month-to-month lease. As the other attorney stated, you could have a valid written lease if the father acted with the authority of the owner.