Do I need anything more than a 30-Day Notice?

[Casey Ames]

I closed on my first rental today and we are going to be living in one of the units. 

The unit we are moving into currently has tenants that I talked to today and will be moving out at the end of July. From the seller, we got credited the tenant's security deposit, prorated rent for June, and last month rent (which will cover July). 

Do I need them to sign a new lease for June and the rest of the July or will a 39-Day notice be enough since I already have rent payments and the security deposit?