Seasoned investors recognize that list price is irrelevant.  

As @Joe Villeneuve indicated, you have to analyze REAL data and insert those real numbers into the analysis.But, the real value of the rule is to recognize that -- assuming you're include management costs and all other typical costs -- if your data suggests that the number is less than 45%, you're most likely missing something. 

* Do you use any calculator that has proven to give you a (pretty) precise calculation of these parameters before closing on a home?

There is no state recognized or special form for withdrawing an offer...just use Word doc titled Withdrawal of Offer with language describing the offer (buyer and seller), date of the offer and the property on which the offer was made.

Guilty until proven innocent on residential loans is how many underwriters do things.You do not have a long history yet of work and the work you do have is seasonal along with you want FHA with little to nothing down.

@Belinda R.You're smart for recognizing your mistakes which means you're growing as an investor.  

  - Those who have the time and patience to build that stuff out and try to focus on SEO as wellThose who don't have those, in the long-run will be better off going w/ a solution that is proven to rank well in competitive markets and convert really well. 

I'm sure private money lenders want a proven track record of your work in order for them to be confident into lending money to your deals.

You have to make them commit after you have proven your initial competency and worth.Guru's, lenders, point takers, brokers, whoever there are these types in every field.

As a Realtor®, I recognize the inherent brainwashing that goes on in the industry with regards to investors, and wholesaling in general.