You need to understand that their are some people that are very negative in nature, they can never tell you the positive side of things, they will always look for excuses for you not to do it.
Some people if you ask dem about their business dey don want to tell, in every business there is a secret and that is the reason why dey don't discuss it out. So don blame them for acting in that manner. Asking one person about a business you want do is not that enough, you have to ask so many people so that dey share their own experience and also in and out of the business. The best I think for someone to do if really he/she want to learn about business is to join them as their boy from there you will be learning it gradually.
So my honest advice is that if you are really convince on what you want to do, just act on it, taking advice from negative minded set of people will only bring you discouragement and loss of interest.
All this negative mindset are part of the challenges of becoming a successful people, you have to prepare yourself for all that will come or you hear, so don't let all this discourage you, some always said this just to scare you or test you to see whether you are ready or not.