Does an employee have to have 3 subordinates in order to be considered salaried?

Huh?? No. As far as I know, he needs only to be full time, unless your workplace has unusual requirements.

I suppose it could depend on company policy but usually it has nothing to do with who or how many people are under you. You are considered salaried when you are not being paid hourly. When you have a set pay for the hours you are expected to work.

For example: someone might earn $50,000 a year as their salary with the understanding that they work a 40 hour work week. If on occasion they work several more hours in a week, they still get paid for what they hired on for. No overtime as someone who is hourly might receive.

Another example: I am paid a salary for teaching. My contract stipulates the number of hours a week I am expected to put in. Without question I put in more than that, as most teachers do, but I still get the salary stated on my contract. I don't "have" to put in the extra time, but it is done nonetheless to do the job well and get everything done that needs to be done.

Agreed, it has nothing to do with how many people you supervise. Hourly folks get a set dollar amount paid for each hour they work. Different labors laws kick in to tell how much they get paid for working more than the usual 40 hours per week, sometimes time and a half. Salaried are paid a set dollar per year, you do not have to be full time to be salaried but most are FT. If a salaried person works 40 hours one week and 75 hour the next week they still get paid the same for the year, no option for overtime when salaried.