I just bought an old (100+ yr old) 6-unit building with a single hot water boiler on a single thermostat. 

Home Inspection - Home inspector found some typical repairs, but the furnace was not working and the thermostat was hanging off the wall.

We have several student accommodations and the prime lease-up windows are late February - April (for those who are very organised and looking for a lease starting in May or September) and June - July (for those who are less organised, or were accepted in to a programme last minute).

Knock on wood I have never had a problem with them doing anything other than using the toilet and leaving lights on along with the occasional thermostat that gets changed to see if the furnace works.

They told me they had a sick child they had to take to the doctor because it was so hot and they had pictures of the thermostat to prove it.

I was first notified by text today, on a Sunday afternoon at 4pm, no one is available today - not the two HVAC services I have existing relationships with - the earliest I can arrange something would be tomorrow, plus, it's pouring rain outside.I'll admit, it's hot out in South Florida now, weather.com says 80 degrees, it's 84 degrees inside their home as reflected by their AC thermostat.

I have to agree with @Roy N.. i provide free Internet myself to my student rentals ( i also control the thermostat and door locks if i have to, from my house - which includes changing the door code with new students, front door only) its a convenience for them and me and helps rent it. as for my other properties i do not provide that service, the tenants pay for that service themselves.

If it's not cooling properly, it's either the fan or the thermostat (most likely).  

If so, require that the new tenant(s) provide(s) proof they've placed the utilities in their name(s) prior to giving them the keys.If the utilities cannot be attributed directly to a tenant, then you will most likely need to bake them into the rent.Another alternative we offer to our student tenants is a utilities budget programme whereby they prepay the utilities each month; we provide them with a copy of the utility bills; every quarter we reconcile.  

Even as a precaution, the thermostats for the heat are programmed not to exceed certain temperatures, so that is controlled to an extent as well.