1. Why are they in this business? To Make money? To change the world? Once you hear that, ask yourself why do you want to be in that business?
2. Who are their competitors? Are the competitors funded? Have any competitors been acquired? Who acquired them?
3. What is their current funding level? How much cash do they have in the bank? How soon do they expect to run out of it?
4. Is the product already designed? If yes, ask for architecture slides, under NDA.
5. Is the product already developed / in development? Ask for the standards they follow? Did their competitors build products based on standards? If the product will integrate within a larger ecosystem, how easy would it be?
6. Who else is already working in the company? Are their any contractors? Are any key people working at other company during the day, that might have similar line of business? Are their any IP infringment issues?
7. Are there any patents / pending patents? Who holds the patents? Is it the company or the founder only?
8. What are their plans of raising money? Will you be given options? If more money is raised, how would your options get affected?
9. What is their market? Is there a sales force? If not, how would the product be sold?
10. What would happen to your health insurance?
11. What is the track record of founders? Call some of their enemies / friends, or place where they worked as engineers.
12. If the product is developed and they have a non-paying alpha customer, who is it? Is that using the product to do what the product is advertised to do? Or are they using it to do something completely different?
13. Do any of your friends work in the same company? Follow them, spy on them. There's nothing wrong with it.
14. Are the founders doing this for the first time? Have they been involved in any other startup?
15. What about the office space? Is it more of show off and less of functional space?
16. Have any analysts covered them? Any reports about them? Any trade journals have covered them?
17. Is the company CEO centric or are other people heard? One way to determine this during interview process, is to hear carefully how many times CEO refers to himself and how many times he refers to team.
18. What was their hiring process? If you were not aware of your strengths and weaknesses, did you become aware of it during this process?
19, Do you think they will hire other people with weaknesses worse than yours?
20. What are you aspiring to learn from this job?