Laundry service for 6 units

[Michael Jackman]

What is your total income from your laundry service you provide your tenants? I'm looking at doing this for a six unit building and I am trying to calculate the total revenue from doing that. 

Do you allow a company to provide the service for you and you receive a payment from them? Do you purchase and maintain your own equipment and collect all revenues?

Which way have you found to be the most effective?

Thanks for your help!