The simplest method would be to take note of the value of all your holdings each time you trade. Then you have simple returns from one trade to the next over your whole portfolio.
Example calculation here: https://money.stackexchange.com/a/98132/11768
It's also possible their YTD return is not weighted properly - if the initial investment had a higher return before the next investment, it would have a higher percentage of your portfolio when you made another investment. If that investment then went down slightly, the absolute decline from the first investment would be larger but you'd hive a slightly ...
I guess a realistic cash flow for home purchase should also include:
Annual maintenance costs
Depreciation due to deterioration
Risks associated with bad tenants
Insurance premiums paid
Insurance $ received
It is important to know that cost basis has very little to do with performance. When a fund (or stock) has distributions that are reinvested, the cost basis goes up while the value generally does not. This is very important and helpful. You dont want to pay capital gains on investment returns that have already been taxed. So, increasing the cost basis ...
Here is how I would approach this. Taking the rates, 1.8% and 2%, as effective annual rates.
deposit = 60000
fees = 15000
house = 145000
loan = house + fees - deposit = 100000
loanrate = 1.8/100 = 0.018
monthlyloanrate = (1 + loanrate)^(1/12) - 1 = 0.00148777
numberofmonths = 20*12 = 240
s = loan
r = monthlyloanrate
n = numberofmonths
d = ...
You have one minor flaw:
So after X years, I would have paid back 116*X/20 of the loan,
Loan principal does not decrease linearly - you pay back very little principal at the beginning (since most of your payment in interest) and it accelerates as you pay it down.
Plus you don't "owe" 116k out of the gate. You only owe 100, so using 116*X/20 would be ...