Delayed security deposit should I accept tenants or find new ones

[Michele G.]

4 tenants (students) were supposed to pay security deposit today for April 1 move in. I have not signed lease yet as I want all signatures, co-signers and security deposit in place. 

They just let me know they can pay half on April 1 and the other half next week after they move in. 

What would you do in this situation and what would you tell the prospective tenants? 
 
thank you 

[Michele G.]

Thank you everyone! I really appreciate your feedback. I thought about delaying the move in date until the security deposit was in hand but then realized if they have issues with the deposit they would likely have issues with rent. I told them I won’t be proceeding with the lease and feel so relieved! Thanks again for your comments! This helped me a lot.