As for why GPs love IRR. It

The value of the apartment is in the cash flow and IRR it can give me.  

When I brought it up to the management company (who was aware that he had moved in), they put him on the lease, but I'm irritated that I had to ask.

Not a super great thing and now I remember why I let my membership expire, it was the irritation at not being able to search for current listings.

That irritates the seller and they often will drop that agent.

Most the listing agent around here all they do is put the house on a bunch of sites including their own to look busy, have irritating auto emailing and voice mail for potential buyers.

Most likely, I'll just disappear once I realize I can't get rich overnight, leaving you exhausted and irritated.

If rash, irritation, redness, or swelling develops, discontinue reading. 

@Mark Whittlesey Good to hear that I'm not the only one that gets irritated by this!

@Lee G.The number looks at the border of good/bad deal, so if it is the best you can get for your area, you may have some decent returns from it.For income tax, you can calculate your Before Tax Cash Flow and then deduct the income tax so you can see what the After Tax Cash Flow like.One question for IRR. It