I just built a bike from parts after several days research. Most components are incompatible which makes it a minefield. The internet makes it seem like their is unlimited choice when in fact there are 1000 incompatible choices, and only one that works and is in your price range. It is absolutely worth it as I now have a bike I can repair myself.
Before undertaking any major project study it intensively, and you'll feel much better about it.
If you can't do the study yourself then find a trusted, disinterested, 3rd party to do it for you. (Of course that entails some study itself...)