Um, OP, I'm a bit confused about you saying "What would happen to them if they knew I vaped?" Do you mean they would be upset, or is vaping at your age not legal where you are?
Because... when I found out my kid was vaping, nothing bad happened, other than he got my support to continue vaping, since he was smoking before... Are your parents very anti vaping or something, is it a cultural/religious thing? Or would your parents just be upset?
If it's the latter, I might get it over with and tell them. If you are living with them still in case you run into other vaping problems it might just be best to get it over with, honestly. You may need their help in some fashion as you transition (for example in a situation like this). I'd be rather upset if my kiddo thought he was dying from something (anything, not just vaping) and felt he couldn't let me know.
If it's the first scenario, it's not fair, just, or moral to subject THEM to possible fines/difficulties etc, because YOU want to vape. Unless you are completely self-sustaining, paying rent, etc., and have no legal ties to them in any way (like health insurance, etc.) then it's not fair kind or just to subject THEM to possible fines and imprisonment and whatever else since they are the owners of their home, not you. I would think hard about that if I were you and the first scenario is the case. Whether you have a good relationship with your parents or not, jeopardizing THEIR well being (financially, legally or otherwise) then you really should consider not vaping, or at LEAST letting them know, so they can decide (if there are risks involved) whether or not THEY wish to take them. Some countries have laws on the books that are rather draconian.
I would come clean. My parents HATED that I smoked at age 18, but I did not hide it. I bought my own tobacco. It was legal, etc. We came to an uneasy compromise, but I wasn't jeopardizing their well being in any way, and my father was a smoker (although not at that time).
Seems to me there are bigger issues here than the nickel, and I rather find that if one tries to do anything "illicitly" there tends to be a lot more anxiety and eventual nasty fall out than just being upfront.
Anna