Anyone that you do this for, must understand that you have no control over the materials that you are using, because you did not supply them, they did. Things can and do break, especially if you are totally altering the use of a piece. Like making a pin into a necklace. You must remove the usually soldered on pin backing and anything could happen to a stone when you are exerting force into the rehabbing equation. As long as you inform your clients of this before you start working, rather than after a stone breaks, things should be okay. If I were working for a total stranger, I would probably use a contract of some sort to cover this eventuality.
It is also hard to give a realistic projection on costs up front because you have no idea how much time might be involved. Wire wrapping presents, for me, the most trouble, because I'm never sure how the time will work out. Just restringing and adding some stones is much easier to estimate. I find that the cost is usually very close to what I would normally charge for say a necklace, because you have all the same time and most of the same materials that you would have if you were starting from scratch. I charge less per hour for my time on rehabs, a little more for my supplies, and nothing for any consult time or design work.
Here are a few examples of rehabs that I have done recently.
This is what I started with - one garnet earring, one pair of amber earrings, one pair of amber earrings with very bad sterling, 2 single amber earrings, one bracelet of pearls missing clasp.
This is what I sent to the client when I was done. An amber, pearl, and black obsidean necklace with 3 amber single earrings hanging from a sterling hoop. A freeform garnet and pearl necklace with the single garnet earring hanging from it. The restrung pearls with a new sterling clasp and some chain to extend the length.
This is another job that I did. This was all done for the mother of a friend of mine.
These gorgeous quartz faceted beads were my friends great grandmother's! They were knotted on silk and it had finally died. I cut everything apart, added a central crystal, and used natural, faceted, rhodolite garnets to separate the crystals, added a nice toggle clasp and voila - these are ready for the fifth generation.
The grandmother's family had a large ranch in California and this stone and the one from the next picture came from mines on this ranch. The jasper above was strung on an ugly black cord, and all I did was do a simple necklace of red poppy jasper beads that set the stone off perfectly. The stone is different on each side, but with this simple treatment, it can be worn either way.
This last piece of jasper, dictated that I had to use gold with it because of the colors in it and I then added brown lava stone and white pearls to make a great necklace.
Whatever I cut off, don't use, anything that is left over, is always returned to the client.
I really enjoy doing this and anyone interested in contacting me about doing this for them can contact me at my shop and I will get back to them ASAP.