Do I need permission from tenant or do I just notify the tenant?

Even though the intent was to hold the buyer harmless, he’s still involved in a suit, which means you need his permission to run that risk on him.Bonding over a lien is done all the time, but it’s not substitution, and it needs the buyer’s permission.

If you feel like you don't want to own a business, investing passively as you have done is ok... and give yourself permission to be ok with it. 

You may be able to approach the current occupants and ask permission to view the inside, but permission is not guaranteed.

I can’t endure even one glimpse of the third.”The man from the country has not expected such difficulties: the law should always be accessible for everyone, he thinks, but as he now looks more closely at the gatekeeper in his fur coat, at his large pointed nose and his long, thin, black Tartar’s beard, he decides that it would be better to wait until he gets permission to go inside.

I would imagine that if your friend created the listing, and then gave you permission, in writing outside of FF, to use it as her agent, you should be able to use their login to update the calendar, write up the description, etc.

Definitely with the landlord's permission.

Any repairs over $500 require my permission first (unless it is an emergency)

Would this RV  allowance overlap with their leased premises, amenities, permissible activities? 

These rules, which include a requirement that sellers set aside a portion of the purchase price for buyer-agent commissions, prohibitions on modifying the commission, and permission to filter listings by commission, all enable NAR, its co-defendants, and its members to maintain buyer-agent commissions at supra-competitive levels unrelated to brokers’ experience or the services provided, steer home buyers away from lower commission homes, and drive out discounters—among other harms."