It is possible, but will potentially be a bit difficult logistically. An example:
You have a potential client ready to sign for your new billing company, but first they want to meet you in person(maybe more than once), and the only time they are available is when you are at work. What do you do? If you manage to figure that out, and they sign as a client, they will want to be able to contact you whenever the urge strikes them...but you are at work, and can't take their calls until you get home. See where I am going with this? Now, if you are honest with them, and tell them you have a full time job for the time being, and can only be available for them at certain times, they will either understand, or they won't.
While I am not trying to discourage you, I am trying to show you how these situations can and most likely will come up. You need to be prepared for them.