For FICO scores calculated from older versions of the scoring formula, this window is 14 days; for FICO scores calculated from the newest versions of the scoring formula, it’s 45 days."

@Nicholas Messinese, It's possible to compute the rental vacancy rate for various markets within the country by using data from the American Community SurveyThe formula is as followsUnfortunately it is not possible to calculate vacancy rates by aggregates such as bedrooms or price since the ACS does not provide the data needed. 

What formula was used?

I have a former tenant that I finally got out and she sold me with a song and dance.

You can know all the formulas in the world but if you don't know what numbers to plug into those formulas, you will be stuck.

Any rough formulas to figure out how much is worth spending on a garage?

I will take the negative too and glean from it. there is no magic formula for this... get a job in the industry earn and learn.. save and then invest.. no ability to borrow basically and no cash will be big time waster for you.. don't waste time on something that is a unicorn and not real. 

It's obviously not an easy formula to weigh, but since you seem to be a bit more neutral about the situation, I guess you (your agent) should be weighing the market and your property, and incremental drops may be the agent's best strategy at the moment. 

@Angelo Wong when the times get tough, the tough get going as the song goes.

I’ve never thought of it that way but will try that formula out when analyzing props.