My understanding is that most lenders will file a mortgage lien on the subject property as soon as the loan is signed so as to preserve their rights, but what if the lender did not do so before the borrower defaulted?...

I’m glad you’ve identified the first vehicle you would like to take.

Even after that time passes it depends on the state what actions you may take but in my state for a relatively modest fee you simply have a constable post a notice and physically remove them 10 days later.

I have had them as well when home inspectors simply do not know the code and we are butting heads..

Most DIYs will simply use a brush and roller due to the simplicity. 

They can simply replicate exactly what you did in the first place.

I would consider taking over a turnkey property there but wouldn't advise investing in a conversion unless you're going super luxury or simply want to enjoy the area yourself frequently.

Many reasons: to encourage/discourage certain economic behavior, to appease a certain industry lobby or some fellow lawmakers or even sometimes a private individual, to buy votes, to balance economic effects of a new law, as well as simply out of incompetence of our lawmakers.

So, let's not put him down simply for asking for help here.

I’m simply going to have to restate what I already said and stick with that. 3K is small as far as a hold back.