Generally, yes, this signals something bad and lowers your chances of being hired rather than increasing them. It suggests that you don't truly understand, or qualify for, the job. Especially very early in the process when they know nothing about you, this is the easiest and safest conclusion to draw. The sooner you do it the more dangerous it is.
If you get through the whole interview process and someone asks you, fairly late on, what you want to make and you say "I know that I'm worth about $100,000 a year but to be honest I really want to work here, so if for some reason you only have $70,000 to offer me, I'll take it" that still would probably not be seen as a positive. There's a chance it might, but it's more likely to be seen as being desperate or in some way unhirable.
Sure, you have low expenses right now. Nobody cares. They won't care later when you have high expenses. Ask for what you're worth and save up money now while your expenses are low. You can use that money later to put a downpayment on a house, or take time off while your children are small, or retire a decade or two before the rest of us. Trying to use your low expenses to make it more likely to be hired is simply not going to work.
What I want is to hire someone who will do what I need. Saving a little money on that person is good, but hiring the wrong person is very very bad. If two candidates are the same I might take the cheaper person, but if they are not the same I will take the better one almost all the time. If the better one wants more than my budget, then perhaps I will reject them, but if the better one is in budget the fact someone else is under budget won't matter to me. To offset that, when I try to imagine why you are willing to work for so much less, I am far more likely to believe that it's because you have no clue what the job really entails, or are desperate for a job and for some reason nobody else will hire you. That minor suspicion is probably all it takes for me to choose someone else.