I would most definitely spray foam the basement walls. 

The termite company said there was moisture (they did the moisture reading after they sprayed a whole can of foam, not sure if it matters) in the wall so it wasn't covered because there was no visible trace of termites on the soil outside (there is a brick privacy wall that butts up to the house). 

I couldn't see any way moisture was gathering at those places, so we just wiped the area down with a bleach cleaning spray (a shoutout for satin finish paint on rental walls!!)

Some of what was found:- glass in front of both crawl spaces (seemingly intentional)- all of the meters were spray painted over- some rooms were inaccessible due to the amount of trash/furniture in the way- registered sex offender on the propertyThankfully, we walked away.

If tenants do that, can the landlord ask for expenses to clean up anything left behind (or from anything similar for example spray-painting something or building furniture)?

New roof, new ceiling, upgraded appliances, spray foam insulation in the crawlspace, added a heater to the crawl space etc... 

A male will spray and every day additional damage piles up.  

The other agreed and suggested that I at least have the inside sprayed so that it would be appealing to an investor.  

The reality is that changing a lightbulb, or the smoke alarm batteries, spraying a little WD-40 on a squeaky hinge or things of that nature to not necessarily constitute adding value.  

I would consider having the siding sprayed, or if you are ambitious, roll/brush it out yourself.