The purpose is to merely illustrate the idea as simple as possible.

The classic example is people who work "under the table" and pay no tax (illegal of course, but just for illustration purposes), and then want to buy a house and are asked for their tax returns... which show no income!

You never stated any where in your post that this was your first transaction, only that you were the realtor, and the 2nd sentence in my post illustrates the issue there. 

It's next to impossible to address in an online forum properly.To illustrate my point, you could be talking about a highly appreciated piece of vacant land in a desirable area or a neglected commercial property in an urban area decimated by Covid or a cash-flowing beach property etc. 

Sometimes a letter of credit or assignment of a CD can be used when fees and guarnatees are higher, which may illustrate good money management on your part along with the appropriate argument as such are insulting your ablity to pay.......LOL

I use very abstract examples to illustrate a general point.

This question illustrates the reason that accountants stay busy.

You can see this in their P&I illustration which is 1/3 of the rent.

Again, this wouldn't fit every operation, I just point out this approach to illustrate that there is no correct answer other than the one that works for you.

See illustration below.