If the landlord has bad health and has to sell to go assisted living, can the land lord get out of the lease to sell the house? WHat kind of agreement would be needed?

If there is an existing lease, the new owner needs to honor it.

There are some circumstances where they can terminate the lease early, but they are rare.

You may be able to negotiate a deal to move out for some consideration.

No they can not get out of the lease, the new owner will be obligated to honor it.

The owner can offer to "buy" your lease out.