I would like to give my staff more hours, but am concerned that by them working more hours, their status could change from part-time to full-time and am wondering if offering paid vacation for example is required by law.
No, benefits are not required by law for full-time workers in Colorado. I strongly recommend that you speak with an attorney to advise you on appropriate offer letters and other materials to protect your business. Business issues are not something to guess about. Good luck with your business.
This answer is for informational purposes only and is not legal advice regarding your question and does not establish an attorney-client relationship.
Lawsuit / Dispute Attorney
No, but that will change soon. The Patient Protection and Affordable Health Care Act also know as "Obama care" will require employers to offer health insurance to full time employees or pay a penalty. The Act takes effect on January 1, 2014 and its effect will depend on how many people you employ, their household income, and other factors. There are many insurance advisors or attorneys who can help. Other than health insurance no employer is required to offer any benefit of any kind. But if you do offer benefits, there are often laws that govern the method of offering and paying benefits which is way to complicated for a short answer.
Answering this quetion does not establish an attorney client relation. The answer is for educational purposes only. You should consult an attorney for your circumstances.
Workers' Compensation Lawyer
I agree with Mr Thomas that nothing is required until Jan. 2014, and then only health care.