How should one deal with fellow students constantly asking for notes?

Giving course notes is probably ok, if you are happy to provide them as a one-off.

If becomes a regular occurrence and the person has no very good reason to not take their own notes (disability or serious family constraints), I think it is perfectly reasonable not to be "their mule". Once is fine, twice is perhaps ok, three times is being exploited. You are not being rude by saying no. It is simply unfair to you for them to exploit you. Don't let them define what is acceptable middle ground, they clearly push the limits to their own advantage.

However, in my time some students produced LaTeXed versions of course notes for everybody to use. If that's what you want to do, it's your perfectly acceptable choice (but it would be a good idea to check with the lecturer - in my time, our lecturers were enthusiastically in favour of a student-typeset version of their lecture which could even serve as a basis of a book; these days, copyright issues may make some lecturers wary of agreeing to that, so - ask!).

Giving out homework is a strict no-no - it's an assessment offence (collusion), and plus, you do not really help them this way to learn.

Addendum: since you are worried that they blame you for later failure, if you give them out make a clear disclaimer that the notes are incomplete and inaccurate and you take no responsibility for their content.

Actually it’s not bad at all to say no even at the first time. I am a student from Netherland and study in University of Padova, Italy. I have asked to few of my classmates to share their lectures and they refused to share by saying “sorry”. And I did not mind. On the other hand one girl said she will share her notes but when I asked to give she made excuses that I will bring tomorrow and then next day and then next day. I really felt bad because she didn’t say NO and actually played with my belief !!!!. So i recommend to simply say NO on a very first time.