In some cases, yes, a verbal agreement can be legally binding and enforceable in court. However, it may be difficult to prove the terms of the agreement without written documentation or witnesses. It is generally advisable to put important agreements in writing to avoid misunderstandings and legal disputes.

Unless this is in your rental agreement you will have a difficult time supporting your side.

A signed offer is an agreement. It would be difficult and disrespectful to attempt to abrogate your committment in a letter.

The Framers came from different states which caused them to have different opinions.

Look at your agreement with the property manager and see what your agreement is. Probably they are not responsible for making the key available, keeping the house clean and so on. It is difficult to control what the house is like when someone else is living there.