You can estimate the initial return by using standard cash flow and ROI formulas.

I think a better formula to base your decision on is cash on cash return. 

Pay the bill yourself, then reimburse yourself by charging the tenants based on a formula.

While there is some truth to what's being said regarding homes being torn down at what appears to be a rather pre-mature time, especially in comparison to North American homes which may be in use well over 100 years, a lot of the information contained is reflective of theory - derived from a predetermined "depreciation" formula established by the government, in essence, to keep the economy humming.The basic formula was determined by taking the age of all the homes that had been razed, and averaging out their age.

what is "RECOGNIZED (TAXABLE) GAIN" and does it even get plugged into a tax liability formula? 

Is there a formula or something to calculate the same?

IRV formula.

However, if others in the area are paying less than what your formula says you should adjust your bid price down to be in line with the market.

There is a very complex mathmatical formula that takes advantage of these lines of credit paying principal down, but also using credit cards with the grace periods for cash purchases like groceries and gas.

Their is nothing wrong with the BRRR formula.