Although I have been a broker for 4 years and have been involved in 6 fix and flips (keeping contractors on schedule, running numbers, being particular with the details, marketing), this is the first time I raised private money, 30k.

That will tell everyone the details of your deal.

Security deposit amountYou can find plenty of examples by searching for "tenant estoppel certificate doc" or exchange "doc" with "pdf" for more options.Here is an example and explanation: https://eforms.com/rental/estoppel-certificate/Some have a lot of legal jargon but this document does not need to be so detailed.

My suggestion is that you give the details to your mortgage guy before you acquire the property so that he/she can estimate future loan for you to make sure the end loan numbers will work.

I know others here could give you a much more detailed explanation.

I don't remember all of the details so I won't besmirch anyone's reputation beyond what I've already said. 

PS Let me know what details I can share that can make this advice easier/more personal to my situation. 

Before I do that, however, I review their (detailed) application and income history in detail.

Jericho Pena without more details it’s hard to say for sure.

If you are detailed and want to understand the business, by all means.