Help! First Time Rental Arbitrage - Mid-term

[Jillyan MacMorris]

I own and live in a 1b/1b condo in Arlington Heights, IL. The unit above me is about to become available and the landlord is willing to rent it to me for $150 below comp rates in the area (about $100 more per month than I pay for my current place). I would like to sublet his unit as a mid-term rental, which could bring in a few hundred dollars of profit per month.

I've never done mid-term rentals, so I'm intimidated! Any advice about how to determine if there is good demand in my area or warnings about the cost-effectiveness of my idea are very welcome! I'm not entirely sure how to run the numbers, and I don't want to sign a lease without reason to believe it will work.