Crm lead score model for start up.

We are developing a crm tool and below are the challenges.

I am working on ml part and we have series of

things to be implemented and in that first is lead score then customer segmentation, churn prediction, and sales forecast.

1. cold start, we don’t have any historical data.
2. Here we are developing tool that should serve for different clients
   across different domains.so can we use one single model or do we
   need develop separate models for each client.

Please recommend what models to use if we use a single large model for all clients.