This is true, especially the losses you may incur in the business. Some people can't stand loosing and business doesn't work that way. You have to be ready to make losses as you learn. Sometimes things may go wrong which you have no control over.
The questions you have mentioned in your post are quite appropriate but I would like to add some few questions.
Start business only if you have a backpack plan, and if you don't have one and still want to start then do ask your self these questions
1. Is taking this risk worthy?
2. Can I afford the loss?
3. What are negative and positive side of my business?
If you are have doubts in any of these above question or even one then do consult someone who is experienced and trustworthy before investing your everything in it.