New Jersey rental property questions

[Kyle Pelech]

I am new to Real Estate but have been doing equations on properties since I was around 14 years old. Every since we took a family vacation to Myrtle Beach, South Carolina; my Dad explained to me how this worked it really amazed me. I am a bit obsessed with finding properties and doing math to see my cash flow and how quick I could pay off a mortgage. Anyway I am now 20 years old with a steady job, I have been saving my money for 3 years and will graduate college this May. I am looking to purchase my first property before this upcoming summer and have a few questions hopefully I can get insight on. 

1. How do you know the property will be rented? Single families scare me, I foresee them being tougher to rent for some reason. There must be a risk, but I see these single families as being more risky as I see them open for renters much more often then a multi family unit.

2. Is it allowed to use an FHA loan and have tenants live in your home with in the first year? I have heard of people doing this, which seems illegal to me.

3. Good or bad idea to buy first rental property off of the MLS? I see cap rates between 8 and 11 percent on most.