In general, you have two options of including different use cases in your market sizing (b2b. commercial, etc):
- Calculate the private use first and then make an assumption re b2c / b2b ratio. E.g. calculate the private real estate in the city and then make an assumption about the commercial real estate as the relative % of private.
- You can add the b2b use cases right in the beginning of your calculations. For example, if you need to calculate the tire market for the light vehicles, you can assume that every 5th car in the street is commercial, thus the total number of cars = # of private cars / 4 * 5. After that, you can calculate the whole tire market
In your particular case, I would try to clarify what exactly b2b means. Are you talking about the companies that subsidize the rides for the employees? (Then you can use the % of your friends who have their rides subsidized. Although B2b, in this case, is already included in the private consumption). Or you are talking about the Uber drivers who use carsharing because they can't afford the car ownership? (Make an assumption re the % of taxis).