Is there a problem with the formula for principal & interest for the first year?

Usually what I would do is make on offer based on a certain formula (ARV x .70 - 30,000 = My offer).So I guess my question is this...should I make an offer based on the value of the land and approximate tear down costs or should I make it based on repairs needed?

@Elizabete De Lima The formula is sometimes Buy-Fixup-Rent then Refi for money for the next deal.

Use the formula to determine Cap Rate:  Net Operating Income divided by the Purchase Price.First,  find out the NOI, which equals total income minus total expenses (not including debt service).If you have the purchase price (what is should sell for) and you know what the rental income is you can determine the cap rate.Example: purchase price is $100,000 and the monthly income is $1,200 or $14,400 per year.

One of the big things that you need to calculate into your formulas is higher vacancy rates.

I need to calculate the roi in an excel sheet i need the formula. say i`m buying and flipping and buying and renting. i saw that for buying and renting i`m making about 8% per year. if the property value increases with another 8% per year how much will the property be worth.

But if you're talking about 95% loans for investing, then those relying on Mike's "Happiness" formula (as if the 2008-9 GFC never happened) might soon be put to the test fairly shortly!...

No formula here, just ballparking numbers. 

Just enter in the following formula and it will tell you what the remaining loan balance is at any point in time, with which you can subtract it from the original balance to see what you have paid off. 

I'll make sure to use that formula every time.