I am also a nurse and understand your clinical detail you describe, and your doubts and “what if’s”. . I had a beloved Golden Retriever that was my happiness and joy. I worked from home and he was my companion at all times. With his crippling illness, the vet asked me ” Are you doing this for you or for him?”. That stopped me. I didn’t want him to go, I didn’t want to be lonely, I didn’t want to take the responsibility for his death, though it would have been peaceful and quick. I realized he cant tell me what he feels, though I saw it with the lethargy and struggle in his eyes. The hardest thing, I did, was to have him put down at home, with me holding him to the end. That was what I did, though I knew it would be tremendously painful for me. You will always miss the dog, so display pictures of her around your home and remember the better times. It will get better! Your dog is at peace and no more suffering. She is smiling from the Rainbow Bridge and wants you to know you did the right thing.

Oh my! I have lied using 8 reasons of your list of 12. Peter says it right- all mostly due to fear and insecurity and self-protection!

You would be legally liable for the lease if you sign it. Should your father be unable to work anymore, the entire rent would be your problem, since he would not have means to pay it. How long is the lease? You would be liable you know? Each and every time maybe you wanted something extra for you or your husband, maybe a a little travel, it couldn’t happen, if you had to worry about paying their rent. You would then have some resentment building up with either you or your husband against you. Is that how you want to start a new marriage? What if his parents wanted you both out of the basement living arrangement? Do you have enough between you to pay for another place to live? It doesnt appear like your husband would accept this arrangement, and if you default on the lease, YOUR credit is trashed next. Are there other siblings or other family members who might help out? Could you pay the entire rent on the lease yourself if stuck with it?
It appears that he is not agreeing to this financial ( legal) arrangement after thinking about it. Maybe you need to make a decision if this is a “dealbreaker” or not? Maybe you need to think what is more important? If your rescuing others is part of your personality, then maybe he wasnt aware of how far you would go for your own family. Maybe he felt that you and he have your own life to start and have a future for yourselves. While living with your parents, I always agree that paying rent of some amount is the sign of a true adult. But depending on the child to take care of the parents with no end in sight, could make a situation that would affect your own future.

JJC- When I am real scared about a situation or something, I ask myself “What is the worst that can happen?” I run it like a movie through my head.Then, I envision the worst, such as the screaming, drama, threats, possible physical abuse. I then anticipate how I will feel and how to react to it in a way that I could feel in control. After running the movie and the “what if’s” in my head, and how I should react to it in a controlled and adult manner, I feel like I can handle it. No surprises, as if that is the worst that could happen, and I handle it, anything else is easier. The unknown and “what if” becomes less unknown and I feel like I can handle it.
My worst “what if” was “Would he threaten or hurt me? Would he kill himself over how I hurt him?” I ran it through my head, how to react to it, and realized that his reaction is his choice, Killing himself means he wont be around for his beloved son, and that he made that choice, We all have choices as our life unfolds. On another note, I would be the beneficiary of his life insurance and I am sure he wouldnt want that!

Maybe if you can anticipate the what if, you can cope and feel less overwhelmed. I haven’t made my move yet, but with the movie played out, it feels like I can handle it, whatever comes up, when I have all my ducks in a row.
(Your lady friend may lose patience, if you keep waffling, and then you have one less support to strengthen you….).

Familiar seems less scary, and actually more comfortable, because that is what we are used to, even if a bad situation. As Inky said, we keep trying to “fix” the original experience and Prove Them Wrong.