If they aren't doing that, they hire an auction comany to dispose of the property.

He has at his disposal a computer (capital) and is using it as a means of economic generation (labor)  which is smart and he has direct access to a community of millions of people by using YouTube (entrepreneurship ability) so your grandson who you scoff at, at his young age, already is understanding the key components to any economic endeavor and he probably learned it from listening to podcasts or watching other content creators. 

Also- in most states, certainly in California, you can get in serious legal trouble for disposing of a tenant's personal property regardless of the situation.

Where do you stand in terms of trying to dispose of the property?

I don't like replacing goods over and over and I'd prefer not to contribute more to the "most things are disposable" mindset (which is why turnover for items such as dishwashers, washer/dryer, fridges, etc. frustrates me because they don't build to last anymore). 

Dispose of all rubbish, garbage, and waste in a clean and sanitary manner – at reasonable intervals – and assume all costs of extermination and fumigation for infestation caused by tenant; not feed straying pets or animals; not temporarily host pets.

My take is, they are basically taking the "disposable funds and applying it to the loan principal.

.), giving you perspective that most residential agents simply don’t have.They operate statewide and even nationally, and they have a network of experienced vendors at your disposal.  

For larger properties, some of our clients run another cost segregation study at the time of sale.2) Partial Dispositions - Taxpayers can carve out and dispose of components removed or demolished from a building.

Although then you are looking at demolition and disposal fees and permits probably, in addition to the new permit(s) for the new ADU.