I am new to investing, so I am when I find a potential property I use the Bigger pockets rental analysis calculator. Trying to find 2/3 unit multifamily that cash flows. When I put in my numbers for vacancy, maintenance and capital expenditures and then I use the 50% rule, my numbers are way off of the 50% rule. 

For example, I am near Madison Wisconsin, I am using Vacancy of 4.5%, maintenance 10% and cap ex at 8%. I know you can only estimate and that every property will be different, but If I am concerned that if my calculations are wrong, I may wind up with a property that costs me money and I can not afford that.  

My question, is it best to stick with using the 50% rule? If that is the case, will I ever find a on market property that cash flows?

2nd question, does anyone know of a group of investors that get together just to get practice on running numbers? I would love to be part of that group.

Thank you.