When to extend the lease and get the rent? special tenant!

[Wen Guo]

Hi fellow experienced landlords -  I have a question for an all up front payment rental tenant. 

I have a tenant that lives in the building before I bought it. The previous landlord signed a 6 month lease and charged him 6 month rent plus 1.5 month deposit for moving in - not sure why, bad credit I assume? Anyway, now there's almost 1 month left, I am thinking about approaching him for the same thing and ask him to pay another 6 month all together again. But how do I do that, do I sign the lease with him right now or do I sign it when the last lease it up in a month? Do I charge him right now or upon the new lease starts? It's a strange term, anyone ever had this kind of lease before?