If there was an offer to rent the house to you for a certain amount, you accepted that offer, and you furnished consideration (something of value) in the form of payment, an enforceable contract was formed and the landlord is obligated to rent to you at that price. It does not matter if they could have or should have asked for more--they did not, and are bound to the agreement they struck.You could enforce your rights in court, through a lawsuit--but bear  in mind that if you can't work matters out with the landlord, the only way to enforce your rights is with a lawsuit. Also, while you could seek what's known as "specific performance"--a court order requiring them to honor the agreement and rent to you at the agreed-upon price--the courts typically disfavor specific performance; the legal system prefers to provide monetary compensation, such as a return of your payment and, if you had to rent a different property at a higher price, possibly the difference in rent, too. Therefore, while you do have enforceable rights, it is not a given that you could vindicate them by forcing these people to rent to you; there is a reasonable chance that your recourse would be some amount of monetary compensation.