If you plan on expanding with more than one owner, then your business will get classified for tax purposes as a Partnership in which case you will begin filing IRS Form 1065 and not IRS Schedule C as a sole owner of the business. Each partner will report their share of the profits (or loss) on their personal tax return. The business will issue Form K-1 to each partner for the calendar year. Partners are not paid a salary although the business may issue guaranteed payments for partners. I would also suggest that you create a partnership agreement to avoid problems down the road. Those are the quick highlights. If need to learn more, I would invest in some of the resources from NOLO > https://www.nolo.com/search?query=partnerships
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I’m not interested in having a co owner, but hiring either 1099 or w-2 employees. I’m just not sure which to do for additional therapists in NYS.