How to run the numbers on a property?

[Michael Guydish]

I plan to do my first deal in the next year or so and I want to start running numbers on properties now to practice and see whats a good deal and whats not a good deal. I plan to do long term rentals with multi-family and single-family properties. My question is how exactly do I do this? Whats the secret formula to see if a property is worth investing in? Any information will help. Thank you!