Multiply $898.82 by 12 months then by 15 years is only $161,787.60. 

Multiply $898.82 by 12 months then by 15 years is only $161,787.60.

Multiply those probabilities by one another, and you have a huge undercurrent of risk ballooning and compounding with each passing month. 

Is there a standard multiplier like say 20% of rent goes to vacancy and opex? 

I believe the one good thing about that spreadsheet is that it can be adjusted by the State you live in. because costs are different in every State the estimate sheet i believe is based on a multiplier for the corresponding State, as most cost estimating books are based. that program does break down a lot of information for you and i think it is a good program, one thing you may want to check is if the program updates every year with current multipliers for the States ( program is probably based on a starting average value for each thing and then the multiplier changes as prices for materials change) and you want to make sure it does that.

Since all the expenses on the calculator were listed as annual, I took the monthly values on the realtor website and multiplied them by 12.I'm very confused on what maintenance costs should be estimated at, as well as what I should put for monthly rent.

Mine's a multiplier of what you pay, and I pay more than that on a monthly basis to navigate all my taxes.

they i multiply by 12 and divide by targeted cap rate. 

Multiply 70% (.07) by $100,000 and you are left with $70,000.

In general, my investors are looking for:mid to high double-digit returnsI'm looking for 2x Equity multipliers (double your money projections) in 5 years or less.I am for opportunities that will give my investors the #triplewinCash Flow, Appreciation and Tax Savings.I might look at 90-100 deals before finding ones I want to invest personally and bring in investor capital.What are you all seeing?