Doing forecasting need to determine:
1) the sources of revenue and the revenue drivers
2) the classification of costs and the costs drivers
3) the nature of costs and their patterns

Then you develop profit and loss + balance sheet + cash flows forecast.

With the above basis, you can perform the cost of customer acquisition per type of revenue per year; the cost of customer acquisition & maintenance / total lifetime revenue for ROI or NPV; break-even, the margin of safety, contribution per sales type; ROCE; market sensitive test; etc.

If you adopt the above, you will somewhat be getting things in the proper place.