This looks like an excel function, but what is the actual mathematical equation?

Oh okay, now the lender has some security just in case you can't pay back the loan...Lets say you are purchasing a property for $100k and for sake of argument and mathematically simplicity the down payment is zero. 

I am just a 21 year old male, studying Applied Mathematics in college.

So end of the day my friends and clients that are the wealthiest that i know have little to no long term liabilities. my bank likes that just fine.. all equity and all cash and very strong earnings..but those of you in the land lording business its completely different you need a certain amount of leverage to scale.For all those mom and pops that are starting to buy SFRs for long term wealth I like to think you pay those off in 10 to 12 years.. whats 100 or 200 a month going to do for you.. pay down those mortgages with others money and get them paid for.. whether that's the smartest mathematical way to do it I don't know.. but like I said everyone I know with limited debt made it through the crash and or sleeps well.but again I am on the down side of my investing career I am not 30 and gung ho like most of you out thereLastly you young investors have so much going on for yourself more than we did in our age.. you blessed to be doing this and most of you if you can control your spending are going to do just fine and be well off in your golden years..

I have previous experience in the marketing field, but most recently have been teaching various mathematics courses at a local high school.

So would you suggest spending some time physically familiarizing myself with a various properties before getting into the deeper mathematical analysis and details?

i guess mathematically it MAY save you some money over the entire course of the loan, but sometimes there is more value then living in the now rather then the calculated savings over the loan...

(Take it from a Mathematics degreed, NASA scientist).You can not take a small sample from a larger environment with a specific set of characteristics and group them into one audience and then conclude that BECAUSE of the characteristics you have seleceted you then project that characteristic over the entire group.Duh.. that obviously doeant make sense.Let me translate this into English.You have a bunch of apples. some red, some green some yellow.You take all the red ones away and place them into one group.

Each bank is different and there is no mathematical equation (unfortunately), but I wondered if there was a general rule of thumb so to speak.

Familiarize yourself with all the mathematical ways to approach prospective deals.