My personal preference is that business is taken care of at the end. I always leave the donation envelope in plain sight. However, either at the beginning or at the end, it doesn't really spoil the mood for me since I know that the lady wants to make sure that she doesn't get ripped off.
When business is taken care of, whether it is at the beginning or the end, I prefer that the lady counts the money in front of me. A few of the ladies have picked up the envelope at the end just as they go to the shower at the end of the encounter to count it in the privacy of the washroom. This makes me somewhat uncomfortable.
I always count the money a few times before the encounter (& placing it in the envelope) and it has only happened to me once where the lady disputed the amount in the envelope. Because of this negative experience, I have sometimes told the lady to count the money in front of me. When the lady counts the money in private or leaves my hotelroom without counting the money, if she disputes the amount, I won't know where the mistake happened.
There was one SP that I've seen numerous times who just took the envelope as she was leaving my hotelroom (after her shower and getting dressed) and she didn't count it in front of me. Even though I counted the money about 3 times before the encounter and placing it in the envelope, it still made me uncomfortable when she did this. On a subsequent meeting that I had with this lady, after the shower, as she was getting dressed, I grabbed the donation envelope from the table and gave it to her and told her explicitely to verify that everything was okay before leaving. She laughed and verified it and said it was fine.
The only time that I don't feel comfortable with taking care of business at the beginning is for overnight encounters or longer encounters. For the 3 overnights that I've had with 3 different ladies, none of them have objected to taking care of business at the end. The donation envelope was always in plain sight.
The first overnight lady did not make any mention of the donation envelope throughout the encounter. The second overnight asked if we could take care of business at the beginning (we always took care of business at the beginning so it was not an "unusual" request) and I told her that because of the amount of money involved, I preferred taking care of it at the end but she was free to verify the money in the envelope before getting started. She didn't verify the envelope at the beginning. If she did, it wouldn't have ruined the mood for me.
With the third overnight lady, she didn't ask about the donation. I told her up front that even though I didn't have a preference when it came to taking care of business (we took care of business at the beginning the first time but for the other 3 or 4 meetings we had met, she always conducted business at the end), because of the amount of money involved, I didn't feel comfortable taking care of business at the beginning. Since we were going out of the hotelroom, I informed her that I didn't have a problem paying for the amount of time used when we left the hotelroom. However, when we actually left the hotelroom and grabbed the donation envelope because I didn't want to leave it in plain sight, I motioned to grab some of the money and asked her whether she wanted a partial payment (for the amount of time already used), she told me that we could take care of business at the end. At the end of this overnight encounter, as she was getting ready to leave, I forgot that I had hid the donation envelope because I didn't want to leave it in plain sight and she felt that it wasn't a good idea to take all the money with me when we left the hotelroom in case I lost it, I remembered before she asked me. When I went to get the envelope and gave it to her, she asked me if she could count it in front of me and I told her that she could and I also mentioned that I separated/grouped the money so she could easily count it. Because she was in a rush to leave because her parking was not paid for, instead of counting all of it (because over 70% of the bills were 20's), she just quickly verified the "groupings" and said that everything was fine.
Another time that I had an issue with giving the entire amount of the donation up front is when I'm not sure how long the encounter will be. For my 2nd or 3rd meeting with Tamara (SexyTamara) where when I made the appointment, I told her that we would meet for 3 hours with the possibility of a 4th hour. She asked for the money up front in the prior encounters so during this encounter when she asked for it at the beginning, I informed her that I would only pay for 3 hours at the beginning because of the uncertainty of the 4th hour. I informed her that before starting the 4th hour, I didn't have a problem paying up front and would pay up front for the 4th hour. She didn't have an issue with this when I actually extended the meeting. In fact, she thought it was somewhat funny when close to the end of the 3rd hour, I went into my pants to get the money for the 4th hour and asked her to stay an extra hour.
The only real issue that I have with taking care of business at the beginning is if the encounter is shortened by whatever reason, it can be difficult to get your money back which is why for long (overnight/trip) encounters or when the timeframe is not firmly set, I feel uncomfortable with taking care of business at the beginning.