Best part was the companionship,friendship and the sex was insane. She still work and did outcalls so it was cool. She had a apartment close to my job so the overnights were great. I even had my clothes at her place. Those that are familiar with the LA traffic will know that to go from Santa Monica to the Inland Empire during rush hour will take you 3 hours or more, at least. Hence the overnights.  
Did it end well? No... She wanted me to leave my wife, my wife finds out..blah,blah,blah you get the ideal, it got ugly so it didn't end well.
In hindsight, we got sloppy and I wish we would have stayed on a P4P. But I loved the overnights.
The "Arrangement" lasted alittle over a years but I was seeing her for about a year on a hooker/John deal before I "moved" in. Then I did the monthly allowance. It made her feel like it wasn't a hooker/John transaction...lol.
This happened from 2001-2003 so it has been a while.
Funny is that we got together in 2013, to try to rekindle the romance, but it wasn't the same and she said " You haven't changed" so she kicked my sorry ass to the curb, which I didn't blame her at all

I had an arrangement but it did not last very long, just over 2 months after a couple of getting to know you dates.  When I went into it the idea was to have the best of both worlds, a fun companion in the bedroom and outside of it.  I think for these to work the personal chemistry and the sexual chemistry need to be equally robust and, in this case, the personal chemistry diminished.  The sex, however, was fantastic.  But alas, I decided to end it as I found myself wanting someone a little more engaging for me on the personal front and it just wasn't there for me. I ended it and it was not well received but we've both moved on.