With the calculator for combined investments one can analyse the capital growth and ROI of a portfolio consisting of savings, equity investments and a house. This computation returns an effective interest rate and the accumulated capital for a given number of years ahead. See also the description of the input and the output fields of the calculator.
In this example I own a house of $ 300000. The value of the house is expected to increase at more than the inflation rate, say 4% per year. The yearly costs of the house are $ 3000 for repairs and $ 1000 for improvements that increase the value of the house. The yearly costs for improvements are expected to increase by 4% each year as well. After 10 years I am planning to move to withdraw most of my money from the house market and move to a much a cheaper house. This move will incur $ 15000 costs.
I also have a savings account with an average interest rate of 4.5% per year. On top of that I have a brokerage account with $ 100000 invested in ETFs. On these equities I am expecting a return of about 8%. Each year I wire $ 5000 to this brokerage account. This yearly amount will increase with inflation. The brokerage firm charges 0.1% of the total balance of the account. Furthermore due to trading I also have 0.6% trading costs.
The table below shows how these numbers should be entered into the calculator. The amounts are divided by 1000.
Field name  Value  Remark 
Number of years  10  Number of years in the computation 
Inflation (%)  3  Expecting 3% inflation 
Category in use  Check only category 1, 2 and 3.  Category 1 is for the brokerage account, category 2 is for the savings account and categorie 3 is for the value of the house. 
Field name  Value category 1  Value category 2  Value category 3  Remark 
Annual value increase (%)  8  4.5  4  
Initial amount  100  25  300  
Yearly amount  5  0  1  Wire 5000 to the brokerage account and spending 1000 on house improvements. 
Indexation yearly amount  3  0  4  Yearly wire to the brokerage account increases with inflation and the house improvement spending will increase with 4% per year. 
Yearly costs ($)  0  0  3  Spending $ 3000 on house repairs. 
Yearly costs (%)  0.1+2*0.3  0  0  Yearly costs for the brokerage account. 
End costs ($)  0  0  15  Costs for moving to a smaller house. 
End costs (%)  0.1+2*0.3  0  0  Yearly costs for the brokerage account. 
The benefit of the rent that did not need to be paid has not been taken into account in this calculation. It could be included by subtracting these imaginary costs from the field Yearly Costs (%), for example by making this field 4 in the house category. In that case the totals are not correct anymore but you do get an idea of the effect of the rent benefit on the computed ROI.
See also the example What is better, buying our house or renting it ?
