@Julie Hill
This sounds like an awesome deal, my favorite kind actually, congrats!
That said, I have had amazing experiences with cash for keys and for sure financially motivating tenants to move out. The key is to have discussions with them, be up front with what is going on and then to have a time line for financial incentives, PLUS get it all in writing and signed.
For example, we just bought an occupied messed up property in Tacoma WA. Prior to purchase we had the month to month tenants sign a new TERM lease that expired at a certain time. However, within the lease we set financial incentives for if they were to vacate the property early, and we gave them a small money bonus for just signing the lease to begin with.
Here is an example from this specific house. Their current rent is $950/m from previous landlord. We paid them $200 for signing the new lease. The new TERM lease is for 30 days. After the term is over, we do not have to go through the very long eviction process since the lease does not renew month to month. We can go straight to the courts and have them out in a matter of 2 weeks tops in our area because of this. The key is, they signed a TERM lease (i keep writing that so that the other BP contributors dont write about "giving notice", this is their notice and they signed it). In the lease, we also gave a $750 incentive if they are out within 2 weeks of signing. Or they get $250 within 3weeks, and NOTHING if they move out at end of the term. At this point, the tenants are on track to be out within the 2 weeks. Im happy to pay the $750, its pretty much the rent we collected already and costs me nothing, but it saves me on time and holding costs AND more importantly, the headache of an eviction.
This is just one example. I have also had great experiences with hoarders by paying for movers, giving them something to sign that says they are out in 2 weeks and they get a nice check from me (with a bonus just for signing the document). The doc basically has them waive all their rights to living there after the two weeks, and them accepting the bonus means they agree to it. They dont get the additional money if they are not out. This is pretty much similar to the term lease example mentioned above.
I AM NOT AN ATTORNEY, so consult your own legal advice for your specific state. All of my agreements mentioned are written by local WA state attorneys that specialize in this line of work. I would advise you to have the attorneys help you too.
Hope this helps.