In-laws live with us. At first it was agreed they would contribute a set amount for ‘rent’ and help out with groceries and incidentals in addition to certain minor chores around the house (taking out trash, refilling ice trays). FIL has apparently changed his mind, sits in the house watching tv all day, in his words “waiting to die”. Does nothing as far as personal care, waits for others to literally serve him meals and most often fix the tv because he punches the wrong button then, like a child, lies about it. (If we know what he did, we can usually fix it without resetting the whole thing). MIL acknowledges his behavior is upsetting, clucks when he won’t write a check for their portion of living expenses, but does nothing. Can we insist he follows through on doctor appontments? How can we get him to understand that living anywhere else would cost him money? Husband tries to reason and gets so frustrated he has stated he’s feels incompetent and sees no way out of our situation.
Other things you mentioned that are upsetting everyone are typical symptoms of Alzheimer's dementia. I encourage both you and your husband to learn everything you can about this disease and also join a local Alzheimer's support group. And start investigating local memory care facilities -- you may not see the need for one in the near future, but it's good to start finding out what's available so you won't be in panic mode if the time comes that you aren't able to continue providing full-time care that can become the equivalent of having 4.5 full-time jobs. And, as a side benefit, it might give your father-in-law opportunity to better appreciate what you're doing for him. Good luck and best wishes.
You also need to try to look at life from his own shoes. It's tough getting old. He can't hop in the car to meet his friends... speaking of friends, probably most have either moved or passed away.... mornings are filled with aches and pains... his eyesight might not be clear and his hearing might be going.
Next time Dad-in-law says "waiting to die", jump in and ask him what kind of funeral does he want and where? Maybe it is time to go to the funeral home and make pre-arrangements, and to the cemetery to pick out the grave site. At least you will know what he wants after the fact, or it might wake him up that he is just being silly waiting to die.
As for FIL and MIL paying of rent, just keep reminding them. In fact, turn off the cable, saying that since they hadn't paid their rent, you couldn't pay the cable bill. I bet he will quickly write a check but first will do a teenager revolt.
Can MIL not write a check herself?
You can insist that FIL follows through on doctor appointments but if FIL doesn't want to go there's nothing you can do about it.
I think as far as your FIL goes he's got it pretty good right where he is with people serving him food while he sits in a chair all day, remote in hand, apathetic and "waiting to die." He sounds like the king of the castle. He knows he'd have to spend his money if they lived somewhere else but he's living for free now so why would he care about moving somewhere else?
Do you and your husband want your in-laws to leave? If so, then you're going to have to make that perfectly clear to them in no uncertain terms. Take your MIL out to look at assisted living facilities. Make sure she brings her checkbook. Invite FIL along as well. Help them make the transition to another place.