How do YOU offer cash for keys?

[Ryan Dossey]

We have 2 properties that we are going to offer cash for keys before we close. Ideally I would rather not have to buy and then figure out how to get them out. Someone recommended a limited durable power of attorney to speak with the "tenants". While others have said it's not necessary being under contract. Both owner will do whatever I need to get the tenants out. 

How do you offer it?

*knock knock knock. Hi my name is Ryan I am purchasing this house. Here is a copy of my purchase and sale agreement. (with price redacted) I would rather help you guys get back on your feet vs. just evicting you and kicking you guys out. I am prepared to offer _______ in exchange for you voluntarily leaving within X amount of days. Conditions are that I am permitted to walk through and photograph property before you move and you get paid after you have moved and I make sure the property is in the same condition. Here is a signed copy of my offer. Please get back to me within _____ hours. 

What do you offer to get them out dollar wise? How many days do you give them to get out? How long do you give them to decide? Can I legally "threaten" eviction?