I have a patron in Thailand who asked me to draw King Bhumibol and Queen Sirikit from a few different photos. It might give you a good idea of what I can do.
I also work from black and white photos - sometimes even working from colour photos it helps to look at a black and white version to focus on tone.
Even candid photos can work well. Leaving out a busy background helps simplify the picture.
Each portrait is my usual size of 75cm x 50cm.
My usual rate for straightforward portraits like these is $100 each. One, maybe two people to draw in each picture is best. Clear large photos work well. I'm more than happy to answer any enquiries.