I think it varies by state & county.

I'm sure rain decreases the effectiveness to some degree.  

(Not completely relevant, but a fascinating tidbit, I think) Now, I think that study was mostly of salaried workers -- being a self employed investor/entrepreneur is a different thing, and I think if a study focused on those folks the results might vary quite a bit.BTW, my current income goal is $12,750 a month (yes, I have a reason for picking that specific number).

I think owning the parks is a vary, very good long term return.

You are never going to know or figure it out to any degree of certainty.

Permit fees can vary widely.

@Michael LebeauIt can vary greatly based on which town you're in since we're just outside of Philadelphia.

I've got a finance degree, and love running the numbers too, but what looks good on paper doesn't always work in real life.

I found them through a well-known "promoter" who utilizes their services.Like others have mentioned, Philly varies vastly block to block.  

Most of their fees are regulated so in my opinion, costs vary little (total closing costs should be 2-3% of total transaction amount).