A wrong targeting of your market study might create wrong and unusable results.
Be careful, some activity sector are highly impacted by laws and local juridictions.
Ask a fair amount of people to obtain good results that will represent your target market.
Be careful with the size of your survey. You have to find a good balance to create a complete survey, but not too long.
Don't be afraid to change your initial offer. A market study will bring knowledge that might push you to evolve your offer.