First off, if your doing custom brushes,get a deposit at least for the Knot you have to buy.
Send pics of the progress of the brush,get okays from the buyer as to shape, material and loft settings.
Count on being stiffed now and than.
I make a brush now and than,if I sell one for say $120 with a $40 Knot that took me 8 hrs to make,I can make more with my shopping cart going thru garbage Bins looking for aluminum cans.