Mr. Dwivedi,
You require to have three basic things in place before attempting such a project :
1. A clear project plan with definitive road-map.
2. Initial boot-finance to fund the start-up phase and operational cash to sustain through the sales cycle before you start making revenue.
3. Operations & sales team.
Once you have these in place, a 50/100 seater should take 60-90 days to go live. Sales & business development begin amost simultaneously so that you have some pilot projects to attempt when you are ready to go live.
I hope that suffices. Please write in if you need more info.
Cheers, Manoj Matai