post of the person who is about to handle sales, marketing and business development for an early stage startup

for any early stage startup, post name of the person who is about to handle sales, marketing & business development???? sales manager or marketing manager or business development manager or junior executive (sales & marketing) or business development executive?

Why is the name so important?

Just employ someone with the skills you need for the company and work out the title later. It is more important to get the company up and running and generating cash to pay the staff and promote the company. What title you give an employee is the least of your worries.

If you are going to employ someone who is only concerned about the job title and status, then they may not be the right employee for your company - especially in start-up mode when it is all hands to the pump to build the company to survive and thrive.