The installers have NOTHING to do with this. Reselling Dish requires DISH NETWORK contracts and they are what they are. Read: insanely stupid and counterproductive and a very good reason so many multi-family houses are hacked to cr*p by installers.
Your father isn't likely to get money from this. What he needs to do is expend the money on having a professional installer come out, place the necessary dishes at the appropriate best place, and wire the feeds down to a lockbox at the side of the building.
Now then, most DBS guys don't know a lockbox from their rear. Lockboxes are cable world stuff. However, such can be gotten and they should be metal. Two of them are needed: one for the switches, amps if any, etc. and one for the interconnect to the apartments.
He's going to want to have at least the Dish 500 for 110 and 119 and the 300 for 61.5 on the building, and the lines going to the first lockbox and a set of DP34 switches. Three in a row for twelve outputs giving four outputs for each of three apartments. People rarely even have four tuners active in multifamily houses, and DHA doesn't do beyond four tuners generally anyways and that's the bulk of Dish work anyhow.
All twelve lines would run through conduit into the second box where they would go to ground blocks and be properly terminated with locking terminators.
When the customer wants to have Dish, they tell your dad, and he has his installer come out and hook them to the ports in the box. When they move out, he has those lines disconnected.
If he charges one penny on this without Echostar agreements, he's breaking the law. Like reselling cable without an agreement. If Dish doesn't have a reasonable program, and they pretty much don't, he'll just have to settle for the fact that having everything prewired and ready to rock and roll on arrival as a big draw. Which it is for an increasing number of renters these days.
I know. I own my own MDU here in CT. My whole neighborhood is hacked to cr*p with E* and DTV never mind what Cox has done.