Potential Tenant and holding fee

[Maclovio Garcia jr]

Hello, my wife and I are first-time landlords and have some new tenants we would like to approve. Both are nurses and meet all of our qualifications; however, their current lease does not end until September 25. They asked if they could move in mid-September. Should we charge them a "holding fee" for the 2 weeks that they would not be occupying the space and have that be applied to first month's rent? Or is there a better way to structure and or go about this? Our property is vacant now and will be vacant for August as well. Should there be a Holding fee clause in the lease upon signing? And when we sign the lease, can we make it effective for September, even though they would be signing beforehand?