I think that I made some improper assumption above. It is not easy to calculate monthly year after year. The better way is to count the whole 25 years of period. Then using the final total margin to reverse back to find out how much percentage of return for each year. Still, I have to make some assumptions here:
(1) Rented dwelling insurance is increased 3% every year, initially 750.
(2) Property tax is increased 2% every year, initially 2,800
(3) Maintenance fee is increased 10% every year, initially 600/year
(4) Monthly paid is 876.89 using 5% mortgage rate with 50,000 down payment
For 25 years, we have:
Rental income = 1200 * ( 12 ? 1 ) * 25 = 330,000
Mortgage interest = 876.89 * 12 * 25 ? 150,000 = 113,067
Insurance = 750 * ( 1 + 1*1.03 + 1*1.03*1.03 + .... + 1*1.03**24 ) = 750 * 35.45926 = 26, 594
Property Tax = 2800 * ( 1+ 1*1.02 + 1*1.02*1.02+ … + 1*1.02**24 ) = 2800 * 32.0303 = 89,685
Maintenance fee = 600 * ( 1+ 1*1.10 + 1*1.10*1.10 + … + 1*1.10**24 ) = 600 * 98.34706 = 59,008
Margin for 25 years = 330,000 ? ( 113,067 + 26,594 + 89,685 + 59,008 ) = 330,000 ? 288,354 = 41,646
However, It is not enough to cover the principal! One has to put more money inside which is 150,000 ? 41,646 = 108,354
25 Years Return rate = 41,646/( 50,000+ 108,354) = 41,646/158,354 =26.2993%
Yearly Return Rate = 0.98%
It is too bad, isn’t it?!