Last months rent used to cover a missed payment?

[Casey Wickline]

Hey guys!

 Quick question! I have renter moving in soon and I'm asking for first and last months rent, and a security deposit. My question is, if for whatever reason she can't pay rent one month, am I allowed to use her "last months rent" to cover that month while I evict her? Are their laws against this or do I just need to cover that specifically in the rental agreement? THANKS.