I would also extend that to CPAs and financial advisers.

You are not only dealing with 3 heirs, you are be dealing with the extended family. 

I paid my mortgage off a few weeks ago and the bank hasn’t officially filed a release or sent me a letter saying it’s paid in full.

I've been talking to some commercial lenders who are willing to extend a line of credit on investment properties in certain conditions with no restrictions on its use like a HELOC.

No step showers, no step entrance, extended doorways, etc., etc.

Each person signing as co-signer is automatically carried over as co-signer on any subsequent lease Renewals or Leases of the company or in the event of Holdover or in the event of Transfer unless Landlord gives a written Release to a co-signer. 31.

Do a Seller Post Occupancy Agreement or execute a lease so it's clear that the terms and conditions of extending that time to him will not allow for a rebate of rent should he leave earlier. 

Another alternative (not as good) is to take the property subject to the electrical system being in proper working order, and have an escrow in place, held by the closing entity, to be released only upon proper inspection and passing results.

Re-lease to qualified Tenants and stabilize the property within 12 months.

The bank will probably want to extend or renegotiate the loan to keep you paying them interest.