Well, the article linked does not say that.

> Services available to the market

Does not mean the business cannot have a one client at a time.

>> Services available to the market >> >> An independent contractor is generally free to seek out business opportunities. Independent contractors often advertise, maintain a visible business location, and are available to work in the relevant market.

But it does mean that. If you aren't free to seek business opportunities, your services aren't available to the market. It's a factor, not the factor.