I've attempted to dispute an appraisal with limited success especially with the Dodd Frank rules in place.

If there is a dispute it is your broker who is liable for the process.

It is also possible that the neighbor could file a suit against your mom and seek a court order to remove the fence, that would require your mom to defend herself in court by claiming the land under the California adverse possession statute.Alternatively, you could advise the neighbor that your mom has the right to claim the property -but as a gesture of good faith, offer the neighbor an amount you feel appropriate in exchange for the neighbor deeding the disputed portion to your mom. 

The city always has an opportunity for you to dispute the taxes.  

What do you do to ensure that the tenant is responsible for security deposit disputes since that is the largest reason for owner lawsuitsHow familiar are you with the newly changed laws that can affect you the owner if they are not used correctly?

This includes info on how much rent they're paying, deposit held by the current landlord, whether they're current on the rents, and any disputes.

What do you do to ensure that the tenant is responsible for security deposit disputes since that is the largest reason for owner lawsuitsHow familiar are you with the newly changed laws that can affect you the owner if they are not used correctly?

If the landlord has not expressed any willingness to mutually find a resolution, you may be better off letting this one go. 

By all means, do so if you are able but do not get yourself involved in the legal dispute.

Regardless of the outcome you will be laying out money or waiting months before a resolution is realized.