Give notice of intent to terminate at the end of the current lease (provide instructions on how they should give you notice)I set a deadline for them to respond so this isn't hanging out there for weeks.

Then you have 6 days to review and terminate if you don't like what's in them.   

Updating the interest rate and loan term in the biggerpockets calculator resulted in projected $404/month cash flow which clears the interest only payment to the seller for the seller financed interest only payment.

Make sure it explicitly explains the process for termination if you are unhappy with their services, but especially if they violate the terms of your agreement.3.

There is almost no scenario where your plan ends well.Give them 60 days notice of termination.

Another question if the lease is written for 60 termination notice, do I have to give 60 for the amended “new” lease or would it still be 30 day notice? 

On the other hand, there's a chance she may stay after her termination date and that could become costly.My policy is to start the eviction process once a tenant is 10 days late.

For example, if the tenants have 7 months remaining on a 12 month lease, you just write the lease for 7 months with the same termination date at the same monthly rate.You also mention running credit checks and screening at the end of their lease term.

selling a rental property does NOT terminate the lease. 

In the event that some red flags pop up during the inspection then you can either negotiate with the seller to cover the costs or terminate the deal and move onto the next one.