As a serial entrepreneur who has created several companies from scratch I can tell you that finding investors is a slow and arduous process, which itself only occurs after you've demonstrated your MVP has traction… which itself is a slow and arduous process. So definitely you should get a job and not pin your hopes on landing investors quickly.

Personally, I wouldn't tell any potential employer that you are working on a startup. What you do in your spare time is completely your business and not theirs (assuming they aren't one of those ridiculous employers that makes you sign an agreement stating that anything you create in your spare time becomes theirs. Obviously you need to avoid jobs like this.). After you've created the MVP and have investors and are ready to make the switch, then you can let your employer know. I did this when I was creating RentACoder.com and my employer surprised me by offering to let me work as much or as little as I wanted to, for as long as I wanted to. This greatly helped me smooth out the transition, and by reducing the risk in that area I could take greater risks on the company itself.

Best of success to you in your endeavor.