It is very good that this sort of question is being asked.
FillSpectre,
I think we are overcomplicating with the issue of the mortgage. Essentially we want to see whether properties are overvalued with respect to other possible investments.
The fact we are borrowing money to buy it makes no difference. A car or a TV is worth a certain amount whether or not we have borrowed money to pay for it. Whether it is worth getting a loan out for is another matter. First we need to find out how much it is worth.
We are really talking about the value of an investment that produces 31k a year and maintains its initial capital in real terms. For the purposes of the excersise, let us assume no capital appreciation or depreciation. We want to remove price speculation from the equation.
So how much is that worth? Really the only way to assess this is to look at alternative traded investments and then compensate for risk if necessary. I would go along with JohnBoy's estimate here.
Other refinements I think would include the effect of inflation, buying and selling costs of both the property and the alternative investment, tax etc.
Now as to the mortgage:
FillSpectre said:
If the sensible valuation is 516k-620k why do you think the bank would value it at 800k?
I would imagine that the bank is mainly concerned with two things:
1. Your ability to pay the mortgage (they may take any number of things into account not just rent on the property)..
2. The
market value of the asset they can reposess if you fail to make your payments.
The important thing to remember here is that the bank is not making the property investment. You are making the investment. The bank is not concerned terribly whether it is a good investment so long as they get their monthly payments. If you don't pay then they can reposess the property and sell it at the market price at that point in time.
Perhaps they should be more concerned with fundamental values, however. In the event of a correction, what they can sieze would be so much less than what people are currently paying for properties, They could also compensate for this risk by charging more interest, of course.
Hope this helps.