The housing is booming here KC , any thing that looks close to right priced right goes quick with multiply offers.http://www.bizjournals.com/kansascity/news/2016/04...

It's time to start multiplying assets !

You could look at other nearby rentals and average the rent/sqft of these listings then multiply this number by the number of square feet of your home to get another estimate.

My assumption is the city assessment stating it was '2.5 stories' simply took the building footprint and multiplied by 2.5.

When you buy a business, you have to determine what is the standard multiplier of the business.  

With an increase of about 7% over last year in Denver (https://www.cpr.org/news/newsbeat/colorado-springs...) and no contraction in sight, scheduled rent increases should continue to multiply that $2,600 of mailbox money forever more, or at least until your portfolio review. 

I agree with @David Krulac - hopefully your property is in one of the 2% RTT areas rather than one of the 4% or 5% RTT areas.The imputed property value used to determine the RTT amount can be found by taking the tax assessed value from the tax assessor, and multiplying (or dividing) by the common leveling ratio that the PA Department of Revenue has posted at their website, for the year and month of the transfer (the values in their table change over time).Once you have that value, and the tax rate for that location, you can figure out how much this screw up cost you ;)

This doesn't appear to be your case though.Appraisers use a gross rent multiplier to determine the income approach in small multifamily properties.

Just take the rent and multiply by 50% and use that as a rough total for expenses in addition to any debt service.The numbers you have above yield total expenses of $33,575 (59% of rents so the rule of thumb isn't needed).  

Well then you take the $900 and multiply it by 12 to give you a year's total income and then subtract your yearly fees from that which is generally about 35%  (10%-Management, 5%-Maintenance, 5%-Vacancy, 15%- Insurance & Taxes.).