So, the formula states the property should bring in 1% of the sales price in rent.

The sheets are filled with formulas that make it easy.

The sheets are filled with formulas that make it easy.

I'd like to know what kind of houses each buyer is looking for, what their formula is so I can accurately cultivate deals, how many deals they're looking to do a year, and what constraints they have.

most important formulas real estate investors use to analyze deals? 

The seller is going to be suspicious if you try to base the price on a mathematical formula with variable inputs.I think the best strategy is offer what you think it is worth and if during due diligence you find it is worth less, explain to the broker why you must retrade.

What is a good formula for IRR. and how do you handle the IRR formula when you are paying cash for a property?

What's the secret to that formula?  

My structures are simple these days 30% down payment at 5% to 8% interest over 30yrs due in 5yrs Of that 30% down payment I'll pay 5% and the seller carrys a 25% second loan(I try to get a non secured 2nd and defer it out to be due at the 5yr payoff, but most sellers are smart enough to want it secured & usually go with a 6 month deferment.)basic you have 1st loan and a second loan to factor in your calculation.Simple Formula example;Total Rent - 1st loan - 2nd loan - insurance - taxes - property management fee - any other expenses that apply to your situation = free cash flow. 

I believe they used some formula that used square footage and number of people per apartment, but unfortunately I don't remember the exact details.