#3 will differ depending on your locale, latitude, etc, but here in the sunny dry southwest, its basically as follows:  Roof coatings, Mini-Split HVAC units, the best windows you can afford (or glass block has a VERY high R-Value) and if you really want to go big, PV/Solar system.  

With any pet, there's more of a chance of incurring additional damages and you also want to consider whether or not the animal will be a nuisance to you and the other tenants within the building.

If it is in decent shape, it may simply be painted over with a proper primer and top coat.  

Don't allow stray animals into your property, they carry fleas. 

Location is Indiana The tenants have a dog and bird in the unit even though the lease explicitly states no pets and there is no addendum allowing an exception for there animals.

Anyone have a strange animals take up residence in a rental?  

8) Is it the norm for the landlord to put a fresh coat of paint inside? 

We usually need two weeks for demo and installation of electrical and plumbing, then a week for inspection, a couple days for insulation, then inspection again and then about a week and a half for rocking, tape, 3 coats of mud, sanding and texture. 

Thieves, vandals, squatters, kids, animals, bugs all of this equals damage to the home and no one is there to monitor any of it.

A fresh coat of paint, a good carpet cleaning, open blinds, and a glade plug in go a long way.