Provide lease now or when full payment is made?

[Jack B.]

I just recently closed on another house that has a MIL apartment. I've rented the MIL (2 days after closing). The tenant can't move in until April 1st, but I agreed to hold the apartment for him for a $400 deposit. I gave him a receipt for said deposit, even though I usually document this on the lease. He's eager to sign a lease, though he doesn't have first months rent just yet (his income is good, but he drives a BMW). I could just tell him I will provide a lease when first months payment is ready. Or is there anything wrong with just signing a lease now? The lease I use is a state provided once that has a grid at the bottom to document payments due, payments made, and payments still receivable and by which date. I could just fill it out and document that he needs to pay first months rent still.