Not a dumb question but maybe a bit premature if you haven't even filed any forms yet. For K1, your income will first come into play only at the interview, maybe 18 to 24 months after submitting the I-129F petition.
Anyway, "household" in the context of the K1 process only includes your children and other tax dependents, if any. Other than those, they don't count towards your household, even if they live in the same house as you. And yes, you (the petitioner) will need to show evidence of enough income to sustain your beneficiary plus all your current household members. The other people in your household are not required to contribute at all, although there is an option (not mandatory) for them to co-sponsor.