From what I've been told most hotels will give you a revenue and a quick estimate is to multiply by revenue multiplier, 2.5-3.5(My Max).

Now take each and multiply by 2 and add 20% for contingency that would be your starting time and money budget. 

If the comp property sold at $1,600,000 and had similar rents then it sold at a 13.75 GRM gross rent multiplier. 

Multiplying first versus subtracting first gives you a different result because of the Please Excuse My Dear Aunt Sally rules.Check out these posts for some more discussion of the 70% rule:http://forums.biggerpockets.com/viewtopic.php?

It is a form of gross rent multiplier that does not take financing into account.

Now that you've discovered the information and networking on Bigger Pockets, I'm sure your productivity will multiply ten-fold!

My rule is to multiply your total monthly income by 50 and that should be your total, all-in cost.  

You then look at your subject property and multiply that $/Sq.Ft by the square footage in the subject house to determine the "retail value" of the subject house, aka the ARV.Some guys will also use the TAX APPRAISAL VALUE as one of the factors that they average together with the comps to get the avg.

(Yearly Gross Rental Income) x 7 x building condition adjustment factor = MAO Yearly gross income can be derived from monthly income by multiplying with 12 months in a year.

My experience with reno is whatever you think its going to cost, multiply that number by at least 2 or 3 times.