If they don't pay, you can pursue them in small claims court.6th - Let the process carry itself out.

I am an out of state note investor, and have a note that is held in my companies 401K Trust, where a neighbor is suing the borrower in small claims court.   

Such as them claiming that they sent money when they didn’t, or claiming they paid more than they really did, or them saying they owe less than they really do. 

It could be a matter of giving them written permission to keep the fence there because adverse possession claims need to be without permission.

Additionally, her house is cluttered and the floors hadn’t been vacuumed or swept in months, so I  am suspicious about her claims of tripping safety and splinters.Questions:- Are her concerns valid complaints?

Your friend may be able to claim interest paid on the underlying loan as a business expense.

Have you ‘claimed’ the house as yours on Zillow.

I also caution in taking on more than double the rehab expense you've incurred in the past - especially with a property that isn't tenant friendly from a parking standpoint; it won't be long before the trekking tenant discovers that trolling for street parking isn't the cruise he signed up for and starts parking in the yard, squeezing in the driveway, or starts claiming defects with the property so he can terminate the lease. 

So she claims they’ve put a lien on her house.

Many times they will claim it's wonderful and then try to hide their worst deals by only showing completed deals.