Does your bellows allow focus to infinity, or just macro? If it allows infinity focus, please describe fully. I'd like to have one
Have used the 50mm f/1,8 on Canon DSLRS since my first EOS 20D. Someone gave me one of the older ones that has the focusing ring at the rear (newer ones have rotating front elements to focus, I believe) The lens was given to me because it would no longer autofocus and cost $65.00 to repair at my local camera repair shop, if I remember correctly. Best investment I ever made other than my wife's wedding ring! Have shot hundreds of "closer than head and shoulders" photos with it, mostly brides. It became a mainstay in my business, and since retirement is making those "awww" photos of my granddaughter.. My plans to use it until I bought the 1.4 version have long since been forgotten. There are several 20x24 prints made with this lens hanging on walls around my town, so the quality of the lens is there.
I sound like a total cheapskate, which I am, although I have no problem spending money when necessary to get the work done. However, I would rather do the job with something a bit less exotic if it can be done. I own and use Canon L series lenses and they do a stellar job, but for a stellar price. This just happens to be one of those places, rare in photography, where one can save money without compromising quality.
I think if you have to ask how much to charge, you haven't the experience to do this well. A wedding is a (hopefully) once in a lifetime experience and there is more to recording someone's wedding than correct exposure and sharp focus. Posing, capturing expressions. I spent years and countless hours in seminars to learn portraiture and wedding photography. If you screw this up, your name will be mud at the ball park.
I have to agree with the others who have said this is a fast track to long term grief for you. I suggest you tell her that you don't yet feel comfortable with such a huge responsibility and refer her to the Professional Photographers of America website where she can find lists of photogs in your area who can handle the job.
Very unlikely to find a $250.00 one, though.
Another vote for the Kelby/Klosowski book. I have it and it gives good, understandable step by step instructions. Ebook copy available from Books-a-Million for $23.00, hard copy $32.00