Yes I do it all the time. I talk to the band by email, try to find out what they want, what they will provide me, then make a guess of the time it will take and if I do a wrong guess and need much more time, then I bite the bullet and don't make the band pay for more. I think it's better when people know beforehand how much it will cost them, instead of finding out in the end: "Ok there's an extra xxxx €".
Booking is made upfront, 50%, then the rest is payed when the mix is done but before sending the lossless audio (revisions are made on 320kbit/s mp3). Some very urgent works, like mastering, sometimes are paid 100% upfront because the band is in a hurry and it takes days for an international money transfer to be done.
I wouldn't send "beeped" material or stuff like that. It takes away from the listening experience, and could hide potential problems where they happen. Plus, I think it sounds like an insult to the band, "I don't trust you", which is a bad climate to work with. Bands trusted you in the first place for sending you money based on a pdf file you sent them, so you have got to trust them in return. Show some respect. That's my philosophy, and maybe one day I will change it, but so far I never had any problem and have like 80 works referenced on my list...