You have fixed costs (lender fee, attorney fee, etc.) and variable costs (taxes, insurance, rent credits).

They offer both fixed-rate interest loans and variable-interest loans that are indexed to inflation and CPI.

But on a duplex 1) Capex is probably the main variable.

There are a lot of variables and moving parts.

To many variables would be left out with 4 classifications.  

There are variables only each person themselves know, like their liquid capital, how many rentals am I buying, how much cash flow do I need, what is the individuals goals that will all determine this. 

These loans come with fixed-rate interest, allowing Real Estate investors to take advantage of potential growth opportunities while mitigating the risks associated with variable-rate loans.

Rents and costs can be adjusted, but zoning and local approval is one variable that you can't really control.If the current zoning on the property is for single family only, does it allows for an ADU?

Commercial Loans typically require a lower LTV than Conventional, eg 75%, but this is both a regional and a lender variable.

Furthermore, some tenants like to know that their costs will be fairly fixed, and having a water bill is one more variable that they will need to account for.