@Account Closed
I use a simple google sheets spreadsheet to calculate my expected income and expenses. Here's an annual list:
Property taxes, insurance ($1000 deductible), Property management (1st months rent + 10% per month after that), and $1,000 miscellaneous expense (home repairs), which is typically an overestimate. I also like to factor in the impact of income tax from the revenue of the property (my accountant told me to factor in 26% - Ohio). Gives me a better overall view. I always take worst case scenario into perspective. An informal rule of thumb I've found is that if two months rent is greater than property tax and insurance combined, the numbers usually work well.
A couple random expenses I've had from my two properties since April (after tenant moved in):
Central air issue, broken screen on screen door, lack of hot water in shower, clogged drain from toilet
I'd be careful in renting to a friend. They may feel you would ben/break the lease because their your friend. That could cost you income down the road.
Let me know if you have any other questions.