You have 20 days to give written formal notice to terminate, but it is 20 days from the end of the month.  

Obtain the services a competent attorney who specializes in evictions.If the tenant is in a local jail, you may be able to get him to sign a formal notice for him to end tenancy by mutual agreement, but you will still be dealing with his possessions.

Where can I find an analysis tool/spreadsheet to work out the numbers and put together a formal/semi-official/convincing package to present to the prospective investors?

It's the Executive Branch of the government, as specified by the US Constitution, equal to the Legislative Branch and the Judicial Branch.

Until there's more judicial interpretstion I would be very cautious and I would guess that a good attorney would tell you the same thing.

The few that I have denied never made it to the showing or formal credit criminal check stage.

Toward the end of the lease, you would give them notice the lease was being terminated (most will continue on a month-to-month basis if not formally terminated.)

In some states, such as Nevada, IF a bank were to exercise the due on sale the Note & DOT automatically become a mortgage requiring judicial foreclosure which takes a minimum of a year during which time the property can easily be refied or sold.  

If such an offer were made and the property goes to foreclosure, and the an injunction is sought in favor of a judicial foreclosure and the offer is presented, the question would then be why did the lender take this to foreclosure when there was an offer to cure the default?

Was a copy of the partnership agreement requested by the lender or was the property just purchased personally with no formal agreement?