Tenant Lease question

[Ryan Cash]

I have prospective tenants that will be accepted by me.  I have the unit available now but want to start the lease on the first of the month.  They are students and school starts on the 25th of this month (5 days before Oct 1)  How would I go about having my 9 month lease start on the 1st of October but allow them to get in the unit by the 25th.  I want to help them out but also don't want the rent to be due on the 25th of every month.  Can I make an addendum to the lease and pro rate their charge for 5 days?