How much does it cost to build a cloud based soft?

Hello

I would like to create an idea management software(similar to https://crowdicity.com/). The software should collect ideas from employees, let them vote, comment on ideas in real time. I probably need a team.
Do you know how many people do I need? Backend, front end, tester?
Do you know how much it will cost me and how long will it take?
Thank you