I am sure you must get plenty of questions about editing - I am wondering how many suggested drafts before approaching an agent might be? Three seems to be a popular number. Do you think there is much benefit to get a manuscript appraised or professionally edited? I am concerned about that as a professional edit might change the sound of my book.
Saying 'three drafts is popular' suggests that publishing runs on the same mathematical principles as the rest of the universe, but the truth is that the industry exists in a temporal fold somewhere between Jupiter and Chiron. If we could reduce everything to equations it would make life so much easier, but we can't. So, no, three is not the right number. The right number of drafts is the right number of drafts - it could be two or ten.
The only thing that I believe is close to a hard-and-fast rule about drafts is that you should give the manuscript time to marinate between each draft - as long as possible, in fact. Weeks and weeks, if not months. You need to come back to it with new eyes each time, and once you think it's cooked, hand it to someone you trust to read it. And by 'someone you trust' I mean someone who's not going to tell you it's wonderful when it's not. The auditions for Australian Idol are littered with people whose friends and family told them that they were wonderful singers when they plainly weren't. As in Idol, so in publishing: you don't want to end up in the gag reel - you want to be in the final twelve.
As for manuscript appraisals: if you can get a recommendation for an appraiser who will give you good editorial feedback, use them. If not, an editor can be useful but it's a considerable investment. It would be good to enter competitions - the writers' centres in each state know what's on - and you may get some feedback from judges.
The whole process of preparing your manuscript will take time; that is all I can guarantee. But the things you learn during that process only need to be learnt once, if you're paying attention, so it's a worthwhile process. Especially if the time you take helps you get published.