Yes, a contract to lease is legally binding in Montana. While some states require both parties to sign the lease in order for it to be executed, that is not the case in Montana.
If the landlord doesn’t sign the lease but accepts rent and allows the tenant to move to the property, it has the same effect as signing the lease. Likewise, if the tenant pays rent and begins to occupy the property, it has the same effect as signing the lease. Leases executed in this way (with only one signature) can only last for one year (MT Code § 70-24-204 (2019)).
The information for this answer was found on our Montana Residential Lease Agreement answers.