How can you accurately calculate operating cost for the ROI?

[Vincent Ames]

Hello everyone. My name is Vincent. I'm 26 years old and am currently working in the medical field for the Navy but my future goal is to own multiple multi family apartment complexes along the East coast. I've been reading a lot about how important the numbers are when it comes to finding the right property but how can you accurately calculate operating cost and up keep for the ROI if you haven't actually bought the property?