do a search for 'memory quilts' you will find many examples---de-constructed clothing is used often in quilting.
as for your charge---you need to decide if you will be adding additional fabrics-or just using the clothing- remember batting,backing & thread-along with any patterns you may use...then you have to decide what your time is worth---all this needs to be discussed with the person you are making the quilt for and a (fair) amount agreed upon before you start....then a 50% deposit should be collected- with the remaining balance paid upon completion of quilt.