i'm saying the following in a general statement sort of way.
i can understand planning for illnesses, they are not unexpected, its just a matter of time. but if a person were to wait until their life became stable no one would ever get pets. life is stable right up until its not. you have to take chances and home for the best. if you go into a relationship, keeping in mind, what do i do if it fails, its more likely yo fail because you holding yourself back. it can be good to consider that before moving in with someone (makes you look at if you are ready to move in and further your commitment to the person) but once the decision is made then you should go in whole heart. that means living like you won't break up and bringing in pets if they are wanted. now, the relationship may work for a year then the people may go their separate ways, it may work for many years, they could get married then get divorced. i always hear that people don't change, well for the most part they don't but sometimes they do and what they become is not who you signed up with. stability in life is only an illusion. we can feel secure in where we're at then the next day be turned on our head. and there are times when people just can no longer care for their animal though they truely love them, either the animal or themselves become too sick to be able to care for them (as a previous example the animal develops an illness -diabetes, heart conditions, hip problems, etc- the the current owner can not afford to care for but perhaps another person could).
as far as back up homes are concerned, they are no different then saving up for that vet bill before the bill comes. sometimes situations change fast and it is comforting that you have a place lined up for your pet should it change so fast that you can not take them with you for a little bit. back up homes do not need to be permanent and are an excellent resource. they also work wonderfully should you become permanently unable to care for your animal properly (due to a life changing illness, accident or death), then you know, no matter what happens to you, even if you are not there to decide yourself, you already have a good place for you animals to go to. you could think of it like god-parents for your pets. i have them for my son, rats and cats and am looking for a good one for my bunny. its just another preparation made in case of an emergency.
being stable as little to do with how prepared a person is to deal with emergencies. emergencies and sudden changes happen all the time. having back-ups and a savings is just one way to prepare for them. but you should not be afraid of emergencies happening so much that you don't put yourself out there, take a risk. i've had friends that their life changed so fast that they found themselves and their family on the street. some were able to keep their pets with them simply because they refused to surrender them to the rescue league, and those pets loved their family and did not suffer for it. others had back-ups for their kids, themselves and their pets. though they were separated they were safe and well and eventually both families were able to get on their feet again though it took considerably longer for the ones that found themselves on the street then the ones that had back-ups they never planned to use.
anyway, it think i've made my point. life changes fast, stability is only an illusion but having escape routes, back-ups plans and the like help people to overcome such situations. you shouldn't be afraid to take those risks. that's what life is, a series of risks. but don't forget while taking those risks to make yourself a safety net as secure as you can.