as a service provider, I dont like to ask upfront but after forgetting my money on 2 occasions I do try to ask politely for the money upfront if I havent met the client before, its nothing to do with rushing the client, its to do with making sure you dont forget at the end, unless of course your not bothered by bad feedback and dont want repeat clients, a perfect client will have the money ready and ask to get it out of the way first, it just creates a good sense of getting down to business without having to try and remember you havent been paid