What exactly should be in this type of contract? Well, firstly you need to be aware of any laws in your country regarding employing people. It is likely these laws will override your agreement so it makes sense to line them up so they match. Then you need to put the basics in there. This might include hours of work, what their role is and how much they are going to be paid. After this, it is a matter of adding some other clauses to protect both you and the employee. This could be to do with dismissal and other situations that might arise.
You are venturing into a business partnership with your best friend, your spouse, or your cousin. If you think you are safe from all the business conflicts that arise in most start up ventures because you know your partner very well, think again. Most conflicts and legal contests are because of this ignorant belief. You have to protect not only yourself but also your partner. Hence it is best for you to draw up a partnership agreement template before you decide to commit yourself.