A question that often comes in financial forums is the following: Most affordability numbers are based on annual income, e.g. affordability for a
house or
car. What happens if one has a large amount of assets, through a windfall or inheritance, but very little income?
Let's take a hypothetical example. Someone is looking to buy a house that costs $200,000. They have $500,000 in assets, but only make $50,000/year. Can they afford the house? On the one hand, they have cash to pay for it outright. But then what about maintenance costs, property taxes, and insurance? On the other hand, the income is too low by conservative standards because house price divided by the annual income is 4, which is much higher than the recommended 2.5 to 3 times.
A crude way to determine affordability is to look at the assets and see what kind of income it is capable of generating. This part can be tricky depending on what type of investments one is considering. As an example, one can use the rate of a 30 year treasury bond to determine how much income can be safely generated. If we use 3% for that number, then $500,000 is expected to generate about $15,000 per year. Add that to the original income and we get $65,000. Now the price to income ratio is about 200,000/65,000 ~ 3.0. This makes the house appear a lot more affordable. On the other hand, if we use the current rate for a savings account which is about 1%, the investment would generate only $5,000 in income annually and would increase the original income amount to 55,000. 200,000/55,000 ~ 3.6 which is still a little high.
If one decides to purchase, whether one choose to finance the purchase or pay cash is a different matter than affordability.
Another related discussion that came up was the following. If one has a portfolio of a certain size, then given that portfolio value fluctuates by 1% on a daily basis, does it mean that 1% of the portfolio is not a lot of money for that person? Taking an example similar to the above one, if one has $500,000 invested and the portfolio fluctuates by $5000 routinely, does it mean that they person can spend $5,000 without thinking twice about affordability?
The best objective answer that I saw to that question was that daily fluctuations in portfolio should be 100 times larger than sustainable average daily spending. In this case, that translates to an average daily spend of $50. This would include meals and all regular
daily spending. Big ticket expenses are fine as long as they are occasional.