Inheriting Tenants with No Security Deposit (NY)

[Ryan Allen]

I closed on my first property (an owner occupied triplex) earlier this month. During the closing process my realtor had notified the seller's realtor to give the current tenants notice that they had to leave.  We were provided with one lease and were told the other tenant currently had no lease and was month to month.

The house was under contract at the end of May. 1 Tenant left at the end of June and was replaced (without my realtor nor I knowing) and a new tenant had moved in on July 1. We had told the seller at the end of July to notify these tenants they had to leave. Given this much notice, the tenants would have to leave by 9/1.

At closing we found out that these are brand new tenants, they had just moved in, and that there is no lease and no security deposit. He said the tenants knew it was likely to come, but he did not tell them they had to leave. After closing I went to the property to start moving in. I met them and had told them the previous owner was suppose to tell them they had to leave by 9/1 and they'd have to leave. Now that it's August, I know they are allowed to stay until 10/1 because I gave them notice this month. 

Two questions - I'm working on a letter to send to them to put it all in writing. I know I should put them on a written lease (month to month) and know I should require a security deposit, how do I ask them for the security deposit and what if they say no? Since they have to be out by 10/1 and I'm telling them that, what would I do if they refuse to pay (or don't have the money)?