ask them if they'll let you have more time to come up with the money. really, the smartest thing to do when renting a house or an apartment is to set aside money for the rent, and use what you need of the rest for necessities, and whatever is left can be used for fun stuff.
If you suspect that the rent will be late, absolutely speak to your rent collector (landlord or super) and let them know. Don't try to avoid them as this will cause them to distrust you and lead them to believe that you are not inclined to pay. If you're up front about it and tell them in advance, they are more likely to accept that you are responsible and trying to take actions to pay them. This will minimize tension and may make them more lenient (no or reduced late fees).