I think it would be a good selling point to have the dish set up and even a cheap freesat box. The whole lot including installation would be less than €200.
The only problem is if a tv licence inspector called the tenants would probably hang you by claiming you own the tv equipment in the house - the dish and box count as a tv. Also, if the dish ever stopped working - even if the signal was bad, you will have your tenants phoning you up to get it repaired.
I had my box for a year now and didn't have any problems, but I know a few people whose sky boxes packed in over the years. Recently a new house was built beside my dad's house and he said it's interfering with the signal so he'll have to move the dish.
I'd recommend freesat over fta because it has a full tv guide. My box has both and although fta has more channels it's easier to use freesat.