I have done 3 projects with this guy, and never had a problem.

I always include property taxes in my analysis of potential properties. 

If you're buying rentals, do a sensitivity analysis and make sure you will cash flow even if vacancy increases or rents drop.

If the appraisal is genuinely flawed, according to an analysis that emphasizes CCCR (Close, Comparable features, Closed, & Recent [yes I made this acronym up]), then by all means dispute it based on that factual data.

I would still calculate for repairs and capex in my analysis, that way I know the place works 10 years down the line, to say nothing of the fact that tenants break stuff.

The numbers have met the projections they gave me.

This created the issue of tenants breaking the lease and a three month rehab project.  

The total cost once its all said and done for the year is 17.6% unless I am calculating this the wrong way to determine the total % you are paying on the OPM over the course of a years worth of projects.

It was around 1.2% when I did my analysis.

I need to develop a Chicago team to make such analysis as you suggest.