Besides the obvious questions of charging per hour plus materials, are there any sort of "guidelines" or other things I should consider when doing textile work? I haven't done much in the way of "huge" and "fibrous" so far.

And by "textile work", I mean a former co-worker's asked me to produce a large purple and blue/turqouise labyrinth on a tarp or something similarly durable for her backyard that can be easily taken out and put away. I need information/advice right away!! Pleeeease!