I am considering investing $25K cash in a healthy ...

There are too many things to consider to answer in this space. However, to hightlight a few consider the following;

The restaurant business has a very high failure rate, so don't invest money you are not prepared to lose.

As a minority investor you have almost no say in decisions made that will affect your investment. So, make sure the written agreements between you and the other investors are specific about how and when profits, if any, will be distributed, how much salary & benefits the managers are allowed to take, etc.

Look at the financial performance of other similar restaurant concepts in similar locations to judge the potential for profit if you decide to go ahead.

Make sure the management has experience, if not in the restaurant business, then certainly management experience in a complimentary field.

There is much more to consider and you might want to consult with a professional.

While the restaurant business is risky and I agree w/ all that was said by Shelly. My experience in airports has been NOT being able to find healthy restaurants. I think it is a great idea and you will have little or no competition in the healthy eating target market.

Good Luck!!! 

The first and most important questions are the ones you ask yourself and answer honestly...What do I know about the day to day requirements of running a fast food business. How will I be successful if I have never worked a day in fast food as an employee, manager, general manager etc. It does not matter how well the franchise trai ning and indoctrination program claims to prepare you for the "journey ahead"...the bottom line is that it is also promotional in nature. You need to know that you are well equipped for success. Start with your personal insight!