The "Business Plan" idea is a good one -- if only to get you to start thinking through what how much many costs are incurred putting two hot dogs, buns, potato salad and cole slaw on a paper plate. Start by imagining the process. You get a phone call from a client -- now pay for the phone bill. You go to the store -- pay for the gas, insurance, wear and tear on the van, and a decent salary for your own time. So it goes -- there's just way more than you imagine.
Food isn't the least of it in the totality of catering. But it's not the be all end all either. And most certainly, "good" food by itself is not nearly enough. You're in a service business, and service -- not food -- is what you MUST supply in order to survice. Your current idea describes "personal chef," more than "caterer." It's as though you've decided to open a shoe store which only sells size 8-1/2, left shoes.
Furthermore, as shroomgirl said, the "ancillaries" of rentals, disposables, flowers, beverages and staff are a huge source of revenue.
You specifically asked,
Well, no one can say for sure... but the answer is almost certainly YES. Unless you've got a bunch of clients already locked in AND are a world class cook, your self-imposed limitations are a quick death sentence.
If you are such an incredibly good cook that the world will beat a path to your door for one or two of your specialties, you should be thinking retail instead of catering. And if you're such a good all-round cook that the world wants you to cater their important events -- they won't hire you unless you do all the other things or associate yourself with a planner.
You might want to think about working with a successful caterer and/or planner before starting your own business.
Ex owner/operator Predominantly French catering; ex cook at a couple of decent joints