Typically, I check with two and get them to compare.

How did their pay compare to the Philipines?

So instead of comparing to the total profit, you're comparing to just the total amount you owe to IRS for taxes.

Comparable sales determine value for residential appraisals, not cashflow. 

so actually I want to propose for lease option to seller;are there any base rules to follow to calculate the rent, option fee, purchase after agreement price comparing current value, etcsuppose a house is valued at 200,000 what should I propose to buy it after 3 yrs lease or 6 yrs lease?

We all have to start somewhere :-)The winter market in MN is relatively slow compared to the rest of the year so don't get discouraged by the inventory you see out there.

Compare to the sitting empty plan, they get to deduct all taxes, insurance, utilities, maintenance, repairs, furnishings, etc etc.

First, percentages lie...especially when you compare them to the Stock Market.I can show you where a 15% yearly return in the Stock market, is blown away by a 5% return in REI. 

I found there are 2 pages more when I compared the new contract and the old contract.

I assume you did your due diligence when making an offer and assessed other comparables to gauge an appropriate asking price?