Rules of Thumb vs Analysis. Where's the crossroads?

[Dustin Smith]

Good morning BP!

I've been inactive for awhile, both in the real estate realm and on BP, since my first deal fell through.  I'm getting my ducks in a row again to get going, but I've run into what may be considered analysis paralysis, but it's more focused on the difference between general rules of thumb and actual analysis when deciding how much to pay for a property.  At what point do rules of thumb become irrelevant and when is it appropriate to actually start asking for real figures when making an offer? 

For instance, I have my eye on a $115,000 triplex with some deferred maintenance that rents out for $1500 per month.  In my area, based on rules of thumb, that's a deal at 1.3% rent to cost.  But at what point do I say that $115,000 is a price I'm willing to pay, versus getting a pro forma or real numbers from the seller and digging into the numbers and finding out what the actual costs are, and ultimately how much I can pay?  Maybe I'm over thinking it, which I've been known to do, but I know my agent has better things to do than contacting every seller that has a property that meets my rules of thumb.  I'm just trying to figure out how everyone else decides what they can offer. 

Thanks!