After reviewing your application, we’ve determined that, unfortunately, we are unable to move forward with your application at this time, as it does not meet our established criteria for income and (other established criteria) We appreciate the time you took to apply and wish you the best of luck in your continued search for a home. 

Property Valuation:Investors look at a variety of factors to determine a property’s value, including comparable sales (comps), rental income potential, and location.

Important to note that the amount available is determined based on the actual stocks/bonds/etfs/mutual funds in your portfolio.

The background check is supposed to identify the amount of risk, then you determine whether you can mitigate that risk or not.

To determine price range, the first step is always figuring our how much you are pre-approved for; and that can vary significantly when you are looking at multi-unit properties because of the additional variable of rental income that can be included in qualifying.

I think another factor here in determining whether its a good investment is your age and your goals. 

.- Value add - When building additional units, what steps should be taken to determine how many can be built?

You should take the feedback given here with a grain of salt and determine which one (if any at all) would work best in your case. 

When you have a duplex and tenants on both sides stay for ten years, it almost guarantees that something isn't right.I would study your market and determine the value of your rental, because I bet you are losing money every month.

What determines if it's a Class A  (b, c, etc.)?