Not calculating maintenance expense could end up being a nightmare.I always estimate (using either the 50%, 1% or square footage rule) the annual maintenance / first year of maintenance fees for a ALL rental property.

Make sure you have a lot of ducks and all fo them in a row. 5 year estimates on revenue and expenses, full business plan, licenses etc etc all in place before you go in.

Quote from @Charles Evans: There are websites that estimate market rent, but they can be off quite a bit.

It is estimated that in 2020 alone $48 Billion was invested in new projects in over 3800 different census tracts.

Have 2-3 contractors look at the job and get written estimates on what it's going to take to finish the job, correct the mistakes, pass occupancy certification etc. use those estimates in your countersuit / mediation process. 4.

Duplex appraised 380 (super ****ing low ball) brings in an estimated 3,900 a month in rents. buyer agreed and SIGNED addendum to purchase at 397,500. day of closing they dont show, tell us they didnt know what they agreed to pay over appraised value and are trying to get us to accept 386k. my agent had me lock in our month to month long term tenant to a year lease for THEIR lender and now they pull this.. they have only 5k in escrow account.. my agent wont reduce his commission from 3%-2% to help bridge the gap. suggestions?? 

The best way to estimate expenses is experience and knowledge of your specific asset type and market.For vacancy, that will depend on your market and the quality/desirability of your type of unit.

Deduct NEW property taxes after you buyDeduct home insurance costsDeduct maintenance percentage, typically 10%Deduct vacancy+tenant nonperformance percentage(we recommend 5% for Class A, 10% Class B, 20% Class C, good luck with Class D)Deduct whatever dollar/percentage of cashflow you wantNow, what you have left over is the amount for debt service.Enter it into a mortgage calculator, with current interest rate for an investment property, to determine your maximum mortgage amount.Divide the mortgage amount by either 75% or 80%, depending on the required down payment percentage - this is your tentative price to offer.If the property needs repairs, you'll want to deduct 110%-120% of the estimated repairs from this amount.Be sure to also research the ARV and make sure it's 10-20% higher than your tentative purchase price.As long as the ARV checks out, this is the purchase price to offer.It is probably significantly below the asking price.

What i do know is i will convert $300k to roth at an estimated 23% fed this year.  

Cashflow – the numbers look good and give me leeway if I have underestimated renovation costs, over estimated rental income achievable or make other mistakes I am not aware of yet!