Sometimes accurate vacancy numbers are hard to get unless you ask for a detailed T-12 or annual RR, and then figure out the vacancy rate yourself.

@Andrew M Bickett because your expenses are not accurate.1) 8% is their monthly management fee, but they also charge a placement fee, which is likely, at least, one month's rent.

On the plus side, their online system is pretty good... all documents properly loaded, reports of who paid and when are accurate and the money is forwarded in a timely manner.  

More sophisticated contractors use various bidding software to get the most accurate quote as possible.

Have a couple different companies come out and give you their numbers on a system you buy from them privately but also a leased system with their guaranteed numbers (most give you the minimum amount of power they will generate for a lease, which are usually accurate.

Zillow has it estimated at 80k but not sure how accurate until an appraisal is done. 

Just wanted to make sure I was accurate to take the liability share into account.

A tentative thought might be to ask folks who are estimating rehab using our calculators if they'd like to share and in return access other people's estimates for rehab projects in their area so that all can improve their ability to accurately estimate costs. 

If everything you say is accurate, I'm not sure why the seller would sell at a discount.

It is a gamble but adjust your price and it can be a winner.