To have an enforceable contract, consideration must be exchanged by the parties; consideration usually takes the form of money, even $1.
Other things could act as consideration, too.
The ‘rent’ consideration could be something like: a promise to do something or refrain from doing it; an exchange of non-monetary property; etc.
But without some sort of valid consideration, a lease agreement would not be an enforceable agreement — so a consideration should be stated within the Lease document.
Get details here on Standard Legal’s Lease Agreement legal forms software.