Congrats to all you "newbies" getting through your interviews and  looking forward to training dates - such an exciting time for you.
I've  taken my 2nd group this week and absolutely loving it! I am on a high  from the minute I get there til well past bed time haha!!
I'm thoroughly enjoying every moment - hopefully this feeling will last a bit longer too!
I  got extremely apprehensive about halfway through the process......I  work full time, my partner & I have hobbies that can often take half  if not a whole day at the weekends - which I was not going to give up, I  don't have children but I do have a partner who still needs feeding  when he gets in from work!!
I was worried I was taking on too  much, I wouldn't be able to do everything Slimming World expect but  touch wood so far it has been fine.
Promotion:
Leafleting 4  times a year (3000 leaflets a time), if you can get enough helpers you  can get it done in a couple of sundays, I had 3 helpers and we split it  over 3 sundays (about 4 hours per sunday) just so it wouldn't be the  whole day taken up with it. But we could do longer hours and get it done  in 2.
Also the school were my group is held put leaflets into the kiddies book bags for me 

Posters  were more of an issue, only managed to get about 25 out, people just  don't want to put them up for you!! and postering on lamp posts etc is a  big no no here.
Hairdressers & the dentist I left magazines for  their customers to read with the group details. You get 20 copies of old  magazines within your franchise fee, but you can buy more for 10p per  copy.
Adverts in local papers / magazines - artwork is done for by  head office, you just email it to the magazine. Shop around for the best  price if you have a couple of publications to choose from.
Editiorial - your story. Mine didn't get published in the local paper, but it did get put into the parish magazine!
Banner  / A frame - luckily my boss lives on the main road through our village,  so he let me put my banner on his fence for 2 weeks prior to opening,  otherwise I wouldn't have anywhere for it. I would have just put it  somewhere on a Friday night & taken it down sunday night before  anyone from the council could take it away!! Risky but I would've done  that to get it up. A frame I just tied to lamp post outside tesco &  other shops in the village, as long as no one was going to trip or run  over it, then left it there all day, picked it up after work.
Community  Activities were another poor area for me. Mums & Tots groups are  held when I'm at work and I didn't want to take too much time off for  this as well as postering, I visited a couple of the main groups and  sent posters & leaflets with a covering letter to the rest - not  very personal I know, but it was better than nothing!
As I was taking  over an existing group I sent letters to all of the "lapsed" members to  say I was taking over and inviting them back. There were 44 letters  sent and so far I've had 3 come back, so was worth it in my opinion.
Car magnets / stickers can be bought to advertise on your car - I blu tacked posters in the rear windows to save a few quid!!!
All  of this promotion takes place over the 15 days before your group opens.  It can seem a bit manic at the time, but if you plan carefully and  realistically you shouldn't have a problem.
I got my 25 new  members by night one and fast tracked, not everyone does and don't be  too hard on yourself if you dont. All you can do is try your best, do as  much promoting in those 15 days as you can, and what will be will be.  My TD was lovely and really understood that I work full time so coudln't  get as much done as I would've liked.
My group only had 20  members when I took over, I had 46 pay on my first night (took about  £120) and 39 pay this week (took about £80), so not bad money wise but I  am getting 40% earnings, if I hadn't fast tracked I would have gotten  about £75 & £50. I don't imagine for a second it will always be like  this, just enjoying it while it is!!!
So if money is an important  factor to you, you need the members, an existing group with a decent  number of existing members would be the way to go. If money is not so  important, then thats irrelevant - enjoy growing your group at your  leisure xx  
The time I spend on slimming world stuff at the  moment is maybe 2 hours tops on a wednesday, counting money for banking,  quick stock take, doing handshake/up load to HO, and looking at &  deciding who needs support this week.
Support on a Thursday or Friday  takes me about 1/2 hour for texts & emails. Haven't had any that I  need to ring yet, so that may increase the time spent slightly.
Training  at Derby is fantastic! There is the cost of travelling & the hotel  to consider, shop around and book early to ensure you get the best deal.
I'm off up there again a week Friday for days 3&4.
I'm not trying to persuade anyone either way, just letting you know my experience so far. 
I wish everyone every success, whether they decide to give it a go or not. You really do have to think about it thoroughly & think about it some more... xx