She was quite upset and started making threats that legally we needed to give her 60 days notice and that she was going to talk to her lawyer.

Most real estate agents do not understand the concept and may see it as a threat to their commission.If you do open a dialogue with the owner, you may want to encourage that his daughter attend your discussions.  

The second included threats to my well being for sending them a letter.

Wills can be contested, the actions of an administrator or executor(rix) can be contested, partition of rights can be filed and the threat of actions can delay a sale, sometimes for years.

Robbery means taking something by force or threat of force, such as with weapons.  

If the rogue contractor does place a lien on your property, which may be a mere threat, challenge it and you may prevail.

I certainly would not mention any type of legal action until you find out a lot more about the situation.It's been my experience that those in bureaucratic positions do not take kindly to threats.

If I evict a tenant, it's like elementary school threats - it's on their permanent record forever and in our area, you can look it up in 30 seconds.

Luckily, we are very close friends and we managed to stick together during the lawsuit threat and the bad feelings about the property.

There are many instances where it may not be a good idea, under threat of foreclosure after notice (illegal transfer BTW) bankruptcy, very little equity with a weak borrower can present problems, when a lender has a reputation of calling notes due, when there are title issues, and when you aren't ready with an exit strategy, selling quickly or buying paying off the underlying mortgage.There are many issues to think about, if you fail to pay as agreed and cause the seller to get dinged on credit, they can come back on you.