That is not a rule, but is certainly likely to be the case.
Usually you will have no choice as to how much the rent is – you have to pay whatever the landlord decides to charge. The only way of controlling how much you pay would be to move to a different place, but that is not normally a very practical thing to keep doing in the short-term.
In addition, most rent agreements are for a fixed number of years and so cannot be changed in the short-term.