[OH] New landlord and getting SSN of existing tenant

[Yash Mira]

I bought my first duplex property recently that had an existing tenant who is planning to stay. I'm good with that, but I don't have have any details of the tenants except name yet. Amongst some details that I need, I need their social security number just in case if I have to evict them and I can cover my behind. How should I go about asking the social security number of them after the fact and they are already settled at the location? What if they ask why I need it? I'm a first time landlord so wondering how to go about this. Thanks!!